s 

S8  7 


UC-NRLF 


i  D    -7  ^    11,  n 


EXPERIMENTS  IN  FIELD  PLOT 

TECHNIC  FOR  THE  PRELIMINARY 

DETERMINATION  OF  COMPARATIVE 

YIELDS  IN  THE  SMALL  GRAINS 


BY 


Lewis  John  Stadi.er,  11.  S.  A.,   \.  Al 


Submitteil  in  Partial  Fulfillment  of  the 

Requirements  for  the  Degree  of 

Doctor  of  Philosophy 


IN   THE 

GRADUATE  SCHOOL 


OF  THE 


UNIVERSITY   OF   MISSOURI 
COLUMBIA,  MISSOURI. 
1921. 


EXCHANGE 


EXPERIMENTS  IN  FIELD  PLOT 

TECHNIC  FOR  THE  PRELIMINARY 

DETERMINATION  OF  COMPARATIVE 

YIELDS  IN  THE  SMALL  GRAINS 


BY 


Lewis  John  Stabler,  B.  S.  A.,  A.  M. 
ft 


Submitted  in  Partial  Fulfillment  of  the 

Requirements  for  the  Degree  of 

Doctor  of  Philosophy 


IN  THE 

GRADUATE  SCHOOL 

OF  THE 

UNIVERSITY   OF  MISSOURI 

COLUMBIA,  MISSOURI. 

192L 


.i<>^£ 


A 


\ 


UNIVERSITY  OF  MISSOURI^  A 

COLLEGE  OF  AGRICULTURE 

Agricultural  Experiment  Station 


BOARD  OF  CONTBOIi 

THE  CURATORS  OF  THE  UNIVERSITY   OF  MISSOURI 


E.  LANSING  RAY, 

St.   Louis 


EXECUTIVE  BOARD  OF  THE  UNIVERSITY 
P.  E.  BURTON, 

Joplin 


H.  J.   BLANTON, 
Paris 


ADVISORY  COUNCIIi 

THE  MISSOURI   STATE  BOARD   OF  AGRICULTURE 


OFFICERS    OF    THE    STATION 

'.  .' : :  •:  f  •  Jb.  mumford,  m.  s.,  director 
J.  a  yo^zi/'TiK'D.,  LL.D.,  president  of  the  university 


STATION    STAFF 

DECEMBER,    1921 


agricultural    chemistry 

C.  R.   Moui^TON,  Ph.  D. 
L.  D.  Haich,  Ph.  D. 
W.  S.  Ritchie,  A.  M. 
E.  E.  Vanatta,  M.   S. 

A.  R.  Hall,   B.   S.  in  Agr. 

E.   G.  SiEvEKiNG,   B.   S.   in  Agr. 

AGRICULTURAL     ENGINEERING 
J.    C.    WOOLEV.    B    .S. 

Mack  M.  Jones,  B.  S. 

ANIMAL    HUSBANDRY 

E.  A.  Trowbridge,  B.  S.   in  Agr. 
L.  A.  Weaver,  B.  S.  in  Agr. 

A.   G.   Hogan,  Ph.   D. 

F.  B.   Mumford,   M.  S. 

D.  W.  Chittenden,  B.  S.  in  Agr. 
A.  T.  EbiNGER,  B.  S.  in  Agr. 

H.  D.   Fox,  B.   S.  in  Agr. 

BOTANY 

W.   J.    ROBBINS,   Ph.    D. 

E.  F.   Hopkins,   Ph.   D. 

DAIRY   HUSBANDRY 

A.  C.   Ragsdale.  B.   S.  in  Asrr. 
W.    W.    SWETT,    A.    M. 

Wm.   H.   E.   Reid,  a.   M. 
Samuel   Brody,    M,   A. 

C.  W.  Turner,  B.  S.  in  Agr. 

D.  H.  Nelson,   B.   S.  in  Agr. 

ENTOMOLOGY 
Leonard  Haseman.  Ph.  D. 
K.  C.  Sullivan,  A.  M. 
O.   C.   McBride, 

FIELD    CJIOPS 
W.   C.  Etheridge,  Ph.  D. 
C.  A.   Helm,  A.   M. 
L.  J.  Stadler,  a.  M. 
O.  W.  Letson,  B.  S.  in  Agr. 

B.  M.  King,  B.   S.  in  Agr. 
A.   C.   Hill,  B.   S.  in  Agr. 
Miss  Bertha  C.   Hite,  A,   B.* 
Miss    Pearl   Drummond,    A.    A.* 


RURAL   LIFE 

O.  R.  Johnson,  A.  M. 
S.   D.    Gromer,   a.    M. 

E.  L.    Morgan,  A.   M. 

Ben   H.   Frame,   B.   S.   in   Agr. 

HORTICULTURE 

V.  R.  Gardner,  M.  S.  A. 
H.  D.  Hooker,  Jr.,  Ph.  D. 
J.  T.  Rosa,  Jr.,  M.  S. 

F.  C.  Bradford,  M.  S. 

H.  G.  SwARTwouT,  B.  S.  in  Agr. 

POULTRY  HUSBANDRY 

H.  L.  Kempster,  B.  S. 
Earl    W.    Henderson 


SOILS 

M.  F.  Miller.  M.  S.  A. 
H,  H.  Krusekopf,  a.  M. 
W.  A.  Albrecht,  Ph.  D. 
F.   L.  DuLEY,  A.   M.« 

R.    R.    HUDELSON,    A.    M. 

Wm.  DeYoung,  B.  S.  in  Agr. 
H.  V.  Jordan,   B.   S.   in  Agr. 
Richard   Bradfield,   A.   B. 
O.  B.  Price,  B.   S.  in  Agr. 

VETERINARY  SCIENCE 

J.    W.    CONNAWAY,    D.    V.    S.,    M.    D. 
L.   S.   Backus,  D.  V.   M. 
O.  S.  Crisler,  D.  V.  M. 

A.   J.    DURANT,    A.    M. 

H.  G.  Newman,  A.  M. 

OTHER   OFFICERS 

R.    B.   Price,    M.   S.,  Treasurer 

Leslie  Cowan,  B.  S.,  Sercretary 

S.  B.  Shirkey,  a.   M.,  Asst.  to  Director 

A.  A.  Jeffrey,  A.  B.,  Agricultural  Editor 

J.  F.  Barham,  Photographer 

Miss  Jane   Frodsham,    Librarian 

E.   E.   Brown,  Business  Manager 


*In  service  of  U.   S.   Department   of  Agriculture,   Seed   Testing  Laboratory. 
'On  leave  of  absence. 


^ 

f" 


CONTENTS 

Page 

The    Problem    6 

Plan  and  Method  of  Investigation   9 

Terminology    9 

Procedure    11 

Work  of   1919    ,. 12 

Work  of   1920   16 

Work   of   1921    18 

Competition  as  a  Source  of  Error  in  Preliminary  Tests   23 

Previous    Investigation    23 

Experimental   Results 25 

Illustrations   of   Effects   of   Competition    26 

Relation   of   Competition   to   Various   Characteristics   of   the   Com- 
peting Varieties   31 

Discussion    40 

Size  and  Replication  of  Plots   43 

Previous    Investigation    43 

Experimental   Results    44 

Size  of  Plots  44 

Replication  of   Plots    SO 

Adjustment  of  Yields  by  Means  of  Check  Plots  54 

Previous    Investigation    54 

Experimental   Results    56 

Method  Used  in  Adjusting  Yields   58 

Relative  Variabihty  of  Actual  and  Adjusted  Yields   60 

Difference  in  Results  Obtained  by  Adjustment  with  Different  Check 

Varieties     63 

Value  and  Limitations  of  Adjusting  Yields  by  Means  of  Check  Plots  71 

Concluding  Remarks 7Z 

Summary     75 

Acknowledgment 77 

References  Cited   78 


TABLES 

Table 

Number  Table  Page 

1  Yields  of  Barley  Varieties  1919 13 

2  Yields  of  Oats  Varieties  1919  14 

3  Yields  of  Oats  Strains  1919  15 

4  Yields  of  Wheat  Varieties  1920 16 

5  Yields  of  Wheat  Varieties  1921  17 

6  Yields  of  Wheat  Varieties  and  Mixtures  1921  18 

7  Yields  of  Oats  Varieties  1921   21 

8  Yields  of  Oats  Strains  1921   22 

9  Relative  Yields  of  Two  Small  Grain  Varieties  When  Compared  in  Al- 

ternate Rows  and  in  Blocks  (Kiesselbach)   24 

10  Correlation  of  Competition  with  Various  Characteristics  in  Barley  Va- 

riety Test  1919   35 

11  Correlation  of  Competition  with  Various  Characteristics  in   Oats  Va- 

riety Test  1919   35 


a 


4735^2 


4  Tables 

12  Correlation  of  Competition  with  Various  Characteristics  in  Oats  Strain 

Test  1919 36 

13  Correlation  of  Competition  with  Various  Characteristics  in  Wheat  Va- 

riety Test  1920 37 

14.     Correlation  of  Competition  with  Various  Characteristics  in  Wheat  Va- 
riety Test  1921   37 

15  Correlation  of  Competition  with  Various  Characteristics  in  Wheat  Mix- 

ture Test  1921 38 

16  Correlation  of  Competition  with  Various  Characteristics  in  Oats  Va- 

riety Test  1921   39 

17  Summary  of  Effects  of  Competition  in  All  Tests  41 

18  Correlation  of  Yield  with  Dates  of  Heading  and  Maturity  in  Variety 

Tests  of  Barley,  Oats,  and  Wheat  42 

19  Yield  and  VariabiHty  of  1-row,  3-row,  and  S-row  Check  Plots  in  Bar- 

ley Variety  Test  1919  45 

20  Yield  and  Variability  of  1-row,  3-row,  and  5-row  Check  Plots  in  Oats 

Variety   Test   1919    46 

21  Yield  and  Variability  of  1-row,  3-row,  and  5-row  Check  Plots  in  Oats 

Strain  Test  1919   47 

22  Yield  and  Variability  of  1-row,  3-row,  and  5-row  Check  Plots  in  Wheat 

Variety  Test  1920  47 

23  Yield  and  Variability  of  3-row  and  5-row  Check  Plots  in  Wheat  and 

Oats  Test  1921    48 

24  Yield  and  Variability  of  3-row  and  5-row  Test  Plots  in  All  Tests  50 

25  Rejation  of  Plot  Variability  to  Size  of  Experiment  Field  in  Wheat  Va- 

riety Test  1920 51 

26  Relation  of  Plot  Variability  to  Size  of  Experiment  Field  in  Wheat  Va- 

riety Test  1921   52 

27  Relation  of  Plot  Variability  to  Size  of  Experiment  Field  in  Oats  Va- 

riety and  Strain  Tests  1921   52 

28  Soil  Heterogeneity  of  an  Experiment  Field  as  Determined  from  Yields 

of  Two  Check  Varieties  53 

29  Effect  on  Plot  Variability  of  Adjusting  Yields  by  Check  Plots   (Kies- 

selbach)     55 

30  Reduction  of  Variability  by  the  Use  of  Check  Plots  Equivalent  to  That 

Probably  Attainable  with  the  Same  Number  of  Plots  by  Replication  .  57 

31  Relative  Variability  of  Actual  and  Adjusted  Yields  in  Barley  Variety 

Test  1919   59 

32  Relative  Variability  of  Actual  and  Adjusted  Yields   in  Oats  Variety 

Test  1919   60 

33  Relative   Variability   of   Actual   and   Adjusted   Yields   in   Oats    Strain 

Test  1919   61 

34  Relative  Variability  of  Actual  and  Adjusted  Yields  in  Wheat  Variety 

Test  1920   62 

35  Relative  Variability  of  Actual  and  Adjusted  Yields  in  Wheat  Variety 

Test  1921    64 

36  Relative  Variability  of  Actual  and  Adjusted  Yields  in  Wheat  Mixture 

Test  1921    65 

37  Relative  Variability  of  Actual  and  Adjusted  Yields   in   Oats  Variety 

Test  1921    66 

38  Relative   Variability   of   Actual   and   Adjusted   Yields   in    Oats    Strain 

Test  1921    67 

39  Relative  Variability  of  Actual  and  Adjusted  Yields  of  Kherson  and  Red 

Rustproof  Oats  Each  in  120  Distributed  Plots,  in  Oats  Variety  and 
Strain  Tests  1921    68 

40  Summary  of   Relative  Variability   of   Actual   and  Adjusted   Yields   of 

Interior  Rows  in  All  Tests  1921  71 


EXPERIMENTS  IN  FIELD  PLOT  TECHNIC 
FOR  THE  PRELIMINARY  DETERMINA- 
TION OF  COMPARATIVE  YIELDS  IN 
THE  SMALL  GRAINS 

L.  J.  Stabler 

During  recent  years  the  investigation  of  the  reliability  of  field 
experiments  has  become  an  important  phase  of  agronomic  research. 
Field  experiments  as  ordinarily  conducted  have  been  shown  to  be 
affected  by  many  gross  errors.  In  the  light  of  these  investigations  it 
has  become  apparent  that  the  results  of  many  of  the  older  experiments 
are  inconclusive  or  even  misleading.  Various  expedients  have  been 
suggested  for  counteracting  experimental  error.  Some  of  these  have 
been  quite  successful,  while  others  have  probably  done  more  harm 
than  good. 

The  pioneer  investigations  in  this  field  have  been  of  great 
value  in  directing  attention  to  the  important  sources  of  error  and  in 
suggesting  possible  means  for  their  control.  Doubtless  at  the  present 
time  most  of  the  major  sources  of  error  are  recognized.  But  the  true 
extent  of  the  errors  and  the  actual  practical  value  of  the  methods  of 
counteracting  them  can  be  determined  only  by  numerous  investiga- 
tions of  experimental  methods  under  different  conditions. 

The  present  paper  is  concerned  with  experimental  error  and  field 
plot  technic  in  preliminary  variety  and  strain  tests  with  the  small 
grains.  The  same  type  of  test  is  extensively  used  in  small  grain  im- 
provement, not  only  in  the  preliminary  testing  of  varieties,  but  also 
in  the  comparison  of  strains  and  selections.  Although  the  small  plot 
test  is  particularly  subject  to  errors  of  certain  sorts,  it  has  a  decided 
advantage  over  tests  in  larger  plots  in  the  possibility  of  extensive 
replication,  which  is  probably  the  greatest  single  factor  in  the  reduc- 
tion of  experimental  error.  It  should  be  possible,  consequently,  to 
obtain  extremely  accurate  results  in  small  plot  tests  without  the  use 
of  large  experimental  areas,  when  the  errors  peculiar  to  the  small 
plot  are  understood  and  controlled. 


(5) 


6   ^•''       , Miss(>xj[8:i  Agr.  Exp.  Sta.  Re:search  BUI.LETIN  49 
• .:  ^-  s.>-  ^J  i  :..t>-        ^jjjj  PROBLEM. 

At  present  the  type  of  plot  most  commonly  used  for  the  pre- 
liminary testing  of  small  grain  varieties  and  strains  is  probably  the 
"rod-row."  The  methods  of  conducting  rod-row  tests  described  by 
Love  and  Craig*  may  be  considered  typical.  The  varieties  or  strains 
are  sown  by  hand  in  rows  one  foot  apart,  usually  opened  and  covered 
with  a  wheel  hoe  or  similar  implement.  The  seed  for  each  row  is 
weighed  out  in  a  quantity  equivalent  to  ordinary  rates  of  seeding  in 
field  practice.  In  harvesting,  six  inches  or  a  foot  at  the  end  of  the 
row  is  discarded,  to  prevent  increase  in  yield  by  reason  of  the  more 
favorable  space  conditions  at  the  ends  of  the  rows.  The  list  of  va- 
rieties is  repeated  in  several  series,  and  the  results  averaged  to  reduce 
the  error  from  plot  variability.  A  check  variety  is  grown  in  every 
tenth  row  to  indicate  the  variability  of  the  field. 

The  use  of  rod-row  tests  involves  several  errors,  derived  principally 
from  the  modified  conditions  under  which  the  plants  are  grown.  The 
object  of  the  test  is  to  discover  the  relative  value  of  the  strains  under 
field  conditions,  and  therefore  any  modification  of  field  conditions 
which  may  favor  some  sorts  more  than  others  introduces  error.  The 
wide  spacing  between  rows,  with  consequently  heavier  seeding  in  the 
row  for  any  given  rate  of  planting;  the  hand  seeding  and  covering,  re- 
sulting usually  in  slightly  ridged  rather  than  slightly  furrowed  rows; 
and  the  growing  of  different  varieties  in  single  rows,  in  competition 
with  other  varieties  rather  than  with  their  own  kind,  are  examples  of 
typical  conditions  which  may  be  expected  to  favor  some  varieties  more 
than  others.  Consequently  the  best  varieties  in  the  rod-row  test  are 
not  necessarily  the  best  varieties  under  field  culture,  even  when  soil  and 
seasonal  variability  are  reduced  to  the  minimum  by  replication  of  plots 
and  repetition  of  the  test  through  a  series  of  seasons. 

Such  sources  of  error  as  those  mentioned  do  not  necessarily  affect 
the  variability  of  the  yields  of  replicate  plots,  as  Kiesselbach'  has 
pointed  out,  and  are  therefore  more  likely  to  escape  notice.  They  are 
systematic  errors  affecting  the  yields  of  replicate  plots  similarly. 
Marked  superiority  of  Turkey  wheat  over  Fulcaster  in  a  variety  test 
in  Kansas  does  not  indicate  the  superiority  of  Turkey  over  Fulcaster 
in  Illinois,  no  matter  how  low  plot  variability  in  the  variety  test  may 
be,  because  the  growing  conditions  in  Illinois  are  different  from  the 
growing  conditions  in  Kansas.  Similarly  the  superiority  of  Turkey 
wheat  over  Fulcaster  in  a  rod-row  test  may  not  mean  its  superiority 
under  field  conditions  in  the  same  locality,  because  here  again  growing 


Experiments  in  Field  Plot  Technic  7 

conditions  are  different.  The  error  in  applying  the  results,  though  of 
course  much  less  in  degree,  is  similar  in  kind.  And,  since  the  rod-row 
test  has  no  purpose  but  to  indicate  the  relative  value  of  the  strains 
tested,  for  field  conditions,  any  pronounced  tendency  to  favor  some 
varieties  at  the  expense  of  others  is  fatal  to  its  object. 

Ordinarily,  however,  the  rod-row  test  is  only  the  first  stage  in 
variety  testing,  and  final  recommendations  are  based  upon  results  of 
tests  under  conditions  which  approach  those  of  field  culture  more 
closely.  When  the  elimination  of  varieties  in  the  rod-row  tests  is 
not  extremely  strict  a  considerable  latitude  may  be  allowed,  and  under 
these  conditions  the  rod-row  test  has  served  a  valuable  purpose.  It 
is  of  course  desirable  nevertheless  to  reduce  these  errors  to  the  greatest 
possible  extent. 

Probably  the  most  important  of  the  errors  mentioned  is  that  arising 
from  the  competition  between  different  varieties,  in  the  single-row  test. 
Obviously  a  variety  grown  in  a  single  row  between  two  different  va- 
rieties may  yield  considerably  more  or  less  than  the  same  variety 
grown  between  two  rows  of  its  own  kind.  Various  expedients  for  re- 
ducing varietal  competition  have  been  suggested.  Sometimes  the  order 
of  varieties  is  changed  in  each  series  to  bring  together  different  va- 
rieties and  thus  tend  to  equalize  the  effects  of  competition;  sometimes 
an  attempt  is  made  to  grow  the  varieties  in  such  order  as  to  bring 
together  those  of  similar  habit,  and  thus  to  reduce  the  effects  of 
competition.  Probably  the  most  effective  method  is  to  grow  border 
rows  which  may  be  discarded,  and  some  investigators  therefore  use 
three-row  or  five-row  blocks,  in  which  the  outer  row  on  each  side  is 
discarded. 

The  principal  objection  to  the  use  of  border  rows  in  the  increased 
area  required  to  test  the  same  number  of  strains,  and  the  large  pro- 
portion of  the  crop  which  is  not  harvested  for  yield.  This  is  par- 
ticularly true  when  3-row  blocks  are  used,  since  in  this  case  two- 
thirds  of  the  field  is  used  for  border  protection.  The  border  rows  may 
be  used  for  seed,  but  two-thirds  of  the  field  is  of  course  much  more 
than  is  required  ordinarily  for  this  purpose.  When  5-row  blocks  are 
used  the  proportion  of  the  crop  harvested  for  yield  is  increased  from 
one-third  to  three-fifths,  though  it  is  an  increase  in  siz,e  of  plot,  with 
some  decrease  in  replication,  so  that  there  may  be  no  gain  in  accuracy. 
There  is  a  possibility  that  the  effect  of  competition  on  the  yield  of  5-row 
blocks  may  be  slight  enough  to  permit  the  harvesting  of  all  five  rows 
for  yield,  particularly  if  the  varieties  may  be  effectively  arranged  for 
the  reduction  of  competition.  At  any  rate,  in  such  plots  the  error 
from  competition  may  be  expected  to  be  much  less  than  that  in  single- 


8  Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 

row  plots,  since  only  two  of  the  five  rows  are  subject  to  competition 
with  a  different  variety,  and  each  of  these  is  subject  to  such  compe- 
tition on  only  one  instead  of  on  both  sides. 

Another  phase  of  the  question  which  should  not  be  overlooked 
is  the  effect  of  adding  border  rows  on  the  error  from  soil  variability. 
If,  for  example,  each  rod-row  is  to  be  protected  from  competition  by 
two  border  rows,  the  test  will  require  three  times  as  large  a  field  as 
the  same  test  without  the  border  rows.  This  can  hardly  fail  to  in- 
crease materially  the  variability  of  the  yields  of  replicate  plots,  to  an 
extent  which  will  vary  with  the  uniformity  of  the  field  concerned. 
The  use  of  border  rows  may  thus  necessitate  the  use  of  an  even  greater 
number  of  replications  for  the  same  degree  of  accuracy,  as  far  as 
plot  variability  is  concerned.  It  is  possible  that  3-row  plots  (whether 
or  not  provided  with  border  rows)  may  require  less  replications 
for  a  given  degree  of  accuracy  than  single-row  plots,  on  account  of 
their  larger  size.  It  is  possible  also  that  5-row  plots,  because  of 
their  size,  may  have  an  advantage  over  3-row  plots  in  reducing  va- 
riability, great  enough  to  justify  in  practice  harvesting  all  five  rows 
for  yield,  rather  than  harvesting  the  interior  three  rows  and  discarding 
the  border  rows. 

The  importance  of  any  practice  that  will  reduce  the  variability  of 
the  replicate  plots  is  thus  increased  when  border  rows  are  introduced. 
A  familiar  method  for  this  purpose  is  the  adjustment  of  yields  by 
means  of  distributed  check  plots.  In  following  this  method  the  yields 
of  check  plots  are  considered  measures  of  the  productivity  of  the 
soil,  which  is  usually  assumed  to  vary  uniformly  between  them.  The 
yields  of  the  experimental  plots  are  adjusted  on  the  basis  of  uniform 
productivity  of  the  field  as  a  whole.  Of  late  this  method  has  rather 
lost  favor  among  agronomists.  In  some  cases  the  adjustment  actually 
increases  rather  than  decreases  the  variability  of  the  replicate  ex- 
perimental plots.  Check  plots  have  not  been  used  extensively  in  ad- 
justing yields  in  rod-row  tests,  principally  because  of  the  great  in- 
crease in  computation  necessary  in  adjusting  the  yields  of  such  a  large 
number  of  plots. 


Experiments  in  Field  Plot  Technic  9 

PLAN  AND  METHOD  OF  INVESTIGATION 

The  experiments  here  reported  were  designed  to  obtain  informa- 
tion on  several  factors  affecting  the  accuracy  of  preliminary  variety 
and  strain  tests,  with  a  view  to  devising,  if  possible,  an  improved 
technic  for  this  important  phase  of  crop  improvement  work.  The 
data  obtained  bear  directly  on  the  following  points: 

1.  The  extent  of  error  from  varietal  competition  in  bor- 
der rows,  and  the  relation  of  such  competition  to  the  charac- 
teristics of  the  varieties, 

2.  The  relative  variability  of  plots  of  1,  3,  and  5  rows,  and 
the  number  of  replications  necessary  for  a  given  degree  of 
precision  with  plots  of  the  three  sizes,  and 

3.  The  effect  on  variability  of  adjusting  yields  by  means 
of  check  plots. 

Terminology. — In  this  report  the  term  plot  will  be  used  to  des- 
ignate an  area  on  which  a  single  vanety  or  strain  is  grown,  in  com- 
parison with  other  varieties  or  strains,  in  other  plots.  The  plot  may 
consist  of  one  or  more  rows.  A  plot  of  more  than  one  row  may  also  be 
referred  to  as  a  block.  The  single  outside  rows  of  the  block  are  the 
border  rows.  A  single-row  plot  protected  from  competition  by  border 
rows,  which  are  to  be  discarded,  will  be  spoken  of  as  a  protected 
single-row  plot.  A  protected  single-row  plot  is  therefore  a  3-row  plot 
with  border  rows  discarded,  and  a  protected  3-row  plot  is  a  5-row  plot 
with  border  rows  discarded.  The  phrase  "3-row  plots  replicated  five 
times"  will  be  used  to  refer  to  3-row  plots  in  five  systematically  dis- 
tributed locations,  not  in  six.  The  area  on  which  a  complete  variety 
or  strain  test  is  conducted  is  spoken  of  as  an  experiment  field,  or  simply 
a  field.  A  group  of  plots  including  one  plot  of  each  variety  or  strain 
tested  is  a  series.  When  four  replications  are  used  there  are  four 
series  of  plots.  The  group  of  contiguous  plots  from  one  side  of  the 
field  to  the  other  constitutes  a  range.  The  ranges  are  separated  by 
alleys. 

Thus  the  field  shown  in  figure  1  consists  of  sixteen  ranges,  each 
range  including  twenty-nine  5-row  (or  protected  3-row)  plots.  Ninety- 
six  varieties  were  tested  on  this  field,  each  replicated  four  times. 
Ranges  I  to  IV,  inclusive,  make  up  the  first  series,  V  to  VIII  the  sec- 
ond, IX  to  XII  the  third,  and  XIII  to  XVI  the  fourth.  Each  of  the 
four  strips  running  lengthwise  of  the  field  and  separated  by  the  check 
plots  may  also  be  considered  a  series. 

All  yields  are  expressed  in  bushels  per  acre  by  weight,  computed 
on  the  basis  of  60  pounds  per  bushel  for  wheat,  48  pounds  for  barley, 


10 


Missouri  Agr.  Exp.  Sta.  Research  BuIvLETin  49 


cn 


17  33 


^9 


6551 


GH 


Zl 


31 


S3 


63  65 


CK 


2541 


5113 


69 


Cli 


29^561 


17 


93  cn 


B 


CK 


18 


M 


SO 


66 


62 


Cli  6 


22 


38 


54 


70 


66 


CK 


10 


26 


42 


56 


74 


90 


Cti 


/4 


30 


46 


62 


16 


94 


CK 


B 


CH 


IS 


35SI 


67  S3 


CH7 


23 


39 


55 


7/ 


87  CH 


274355 


75 


CH 


15 


31  &1 


63 


13 


95 


Cli 


B 


cn 


20 


36 


5-268 


e^CKa 


24  40 


56 


72  88 


ClilZ 


26 


M 


60 


76 


92 


CH/6 


32 


4<9 


6460 


96  Cti 


Ch 


21 


37 


53 


69  65CK  9 


2541 


57  7^59 


CKl3 


29 


45 


77 


93 


Cti  I 


17 


33 


45 


65dlCK 


B 


CK 


22 


36 


5^70  66CK 


10 


26 


42 


58 


7^ 


90 


Ct\l& 


30 


46 


62 


18 


34C/i  2 


18 


3^50 


66 


82 


cn 


B 


Ch 


23 


39 


5571  676/1//  274J 


59 


75 


91 


CKl5 


31 


47 


63 


79 


95  CK 


19 


3551 


61Q3GK 


B 


CH 


2^^S6 


72  66CK/2 


28 


H6076 


92 


CKl6 


32 


64 


m 


96 


CK 


20 


36 


52 


68 


diC/f 


a\ 


25  fl 


57 


73  59 


CK/3 


291-5 


61 


7793 


CK 


17 


33 


45 


65 


81 


CK 


21 


3753 


6985 


CK 


B 


c/i/0 


26^256 


Tf 


90CKl^ 


30 


^6 


62 


76 


9i 


CK 


16 


3450 


66 


82 


CK 


22 


36 


5^70 


66  CK 


B 


CKli 


27  f 3 


59 


75 


$1 


CKIS 


31 


4763 


79 


95 


CK 


19 


35 


Si- 57  63 


CK 


2339557187 


CK 


BCn/2 


^d'h^eo 


76 


92 


OK  16 


32 


4S 


6^80 


96 


CK 


zo 


36 


52 


6884  CK  6 


24  4056 


72 


66 


CK 


BCK/3 


29  4561 


77 


93 


CH 


17 


33 


49 


65 


61 


CKs 


21 


31 


53  69 


55 


CK 


25 


4/ 


57 


7369 


CK 


BCKli 


30^6 


6278 


94 


CK 


/8 


34 


50 


66 


82 


CK 


22 


38 


54 


7086CKI0 


26 


42587^ 


90 


CK 


B 


CKIS 


31 


47637S 


95CK  3 


19 


35 


51 


6183 


CK 


23 


39 


55  71 


61  CK// 


274359 


75 


9/ 


CK 


BCAI6 


32 


4^ 


64 


Q096CK& 


2036  52 


6&&tCK 


24 


405^ 


72  88 


CK/2 


28 


44  60  76 


92 


CK 


Figure  1.— Planting  Plan  of  Wheat  Variety  Tests  1920  and  1921. 
Legend:  B,  border.  CK,  check.  Numbers  1-96,  planting  numbers  of  varieties 
tested  as  given  in  Tables  4  and  5. 


^Experiments  in  Fiei.d  Plot  Technic  11 

and  32  pounds  for  oats.  The  measures  of  variability  used  are  the 
average  deviation,  the  standard  deviation,  and  the  probable  error. 
These  were  computed  according  to  the  following  formulae: 


in  which  A.D.  =  average  deviation,  o-=standard  deviation,  E  =  prob- 
able error  (of  a  single  determination),  d  =  the  deviation  of  a  single 
variate  from  the  mean,  and  n  =  the  number  of  variates.  The  correla- 
tion coefficient  r  was  determined  by  the  formula 

^^/2(dA)\/J_\ 

\       n       /  \<rx<^y/ 
and  the  probable  error  of  the  correlation  coefficient  Er  by  the  formula 

.6745  (1  —  r") 


E,=+: 


vs- 


The  tests  reported  are  of  two  kinds,  variety  tests  and  strain  tests. 
The  variety  tests  were  comparisons  of  commercial  varieties,  most 
of  which  were  taxonomically  distinct.  A  number  of  pure  line  selec- 
tions were  included  in  the  wheat  variety  tests.  The  strain  tests  were 
comparisons  of  a  considerable  number  of  commercial  lots  of  the  same 
variety  obtained  from  different  sources.  These  strains,  so-called  for 
convenience,  are  not,  except  in  a  very  few  cases,  pure  lines.  Some  of 
them  are  possibly  identical,  and  all  the  strains  of  any  one  variety  are 
of  course  very  similar,  since  they  are  taxonomically  the  same. 

Procedure.— In  the  seasons  of  1919,  1920,  1921,  tests  of  va- 
rieties and  strains  of  oats,  barley,  and  wheat  were  conducted  in  blocks 
consisting  of  five  rows  ten  inches  apart  and  usually  18  feet  long. 
From  24  to  96  varieties  were  included  in  each  test,  and  from  three  to 
six  (usually  four)  replications  were  used.  The  planting  order  in  each 
case  was  designed  on  a  plan  similar  to  that  illustrated  in  figure  1. 
It  will  be  noted  that  the  check  plots  were  in  continuous  strips,  that 
each  variety  was  represented  in  each  quarter  of  the  field,  whether 
divided  from  east  to  west  or  from  north  to  south,  and  that  in  all 
four  series  each  variety  occupied  the  same  position  with  relation  to 
the  check  plots,  and  had  the  same  varieties  adjoining  it  on  either  side. 


12 


Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 


The  rows  in  some  cases  ran  east  and  west,  and  in  some  cases  north 
and  south. 

All  these  plots  were  seeded  with  a  5-row  nursery  drill,  built  from 
plans  furnished  by  Professor  T.  A.  Kiesselbach  of  the  Nebraska  Sta- 
tion. This  is  a  hoe  drill  designed  for  rapid  and  thorough  cleaning 
between  plots.  Photographs  of  it  have  been  published  in  reports  of 
earlier  work  on  field  plot  technic  at  the  Nebraska  Station  (Mont- 
gomery" page  57,  and  Kiesselbach  °  page  16).  Its  use  resulted  in  uni- 
form seeding  and  covering  and  accurate  spacing  between  rows,  with  a 
close  approach  to  ordinary  field  conditions  in  the  state  in  which  the 
field  was  left  after  seeding.    Each  field  was  seeded  in  a  single  day. 

All  plots  were  harvested  by  hand  with  sickles,  a  foot  at  each 
end  of  each  row  discarded,  and  the  remainder  (usually  16  feet)  tied 
in  a  bundle  and  hung  in  a  ventilated  shed  to  dry.  In  1919  and  1920 
each  row  was  bundled  and  threshed  separately;  in  1921  the  border 
rows  of  each  5-row  block  were  bundled  separately  and  the  three  in- 
terior rows  bundled  together.  Yields  were  determined  by  weighing 
in  grams  at  the  time  of  threshing.  All  final  yields  were  converted 
to  bushels  per  acre  and  are  so  expressed. 

Work  of  1919. — In  1919  tests  were  conducted  with  barley  and 
oats.  Thirty  varieties  of  barley  were  grown,  each  in  3  replicate  plots. 
The  test  comprised  three  ranges  of  185  rows  each,  including  21  check 
plots,  or  one  in  every  sixth  plot.  The  barley  was  drilled  at  the  rate 
of  eight  pecks  per  acre,  on  March  21,  in  rows  running  north  and  south. 
The  rows  were  14  feet  long  and  10  inches  apart.  They  were  cut  to  12 
feet  in  harvesting.    The  planting  plan  is  shown  in  figure  2.    Conditions 


CA 


10  ch 


a 


17 


Z0CmiZ2Z3Z^ 


Z5CK 


2621Z82930CKB 


CKZI 


21 


23  2i 


25 


CH26 


27232930 


CM  I 


Cii 


cn 


on 


17 


19  ZO 


CK  B 


Oil  I 


15 


OKI 6 


/7/S 


20  CKZI 


22  S3  24  25  OH  26  27  28  29  30  OH 


CH6 


9  10  Cf\ 


Figure  2.— Planting  Plan  of  Barley  Variety  Test  1919.  Legend:  B, 
border.  CK,  check.  Numbers  1-30,  planting  numbers  of  varieties  tested,  as 
given  in  Table  1. 

were  fairly  favorable,  and  the  yields  of  the  adapted  varieties  were 
slightly  higher  than  the  average  obtained  under  the  conditions  at  Co- 
lumbia. Two  varieties,  Italian  and  Australian  White,  gave  extremely 
low  yields  and  were  excluded.  Another,  Sandrel,  was  represented 
only  in  two  series,  and  was  also  excluded.    The  yields  of  the  remain- 


Experiments  in  Fiei.d  Plot  Technic 


13 


ing  27  varieties  are  shown  in  Table  1.  The  planting  numbers  given  in 
this  table  correspond  to  those  shown  in  the  diagram  of  the  field  (figure 
2.) 


Tabi^e  1. — Yields  of  Barley  Varieties. 
In  Bushels  per  Acre.   1919. 


Planting 

Average  Yield 

number 

Variety 

3  interior  rows 

5  rows 

1 

Hanna  906 

12.55 

12.57 

2 

Steigum  907 

19.90 

19.65 

3 

Luth  908 

23.65 

23.40 

4 

Eagle  913 

20.40 

20.13 

5 

Italian  914* 

6.70 

6.57 

6 

Servian  915 

19.85 

19.86 

7 

Odessa  916 

13.75 

13.41 

8 

Lion  923 

21.75 

22.14 

9 

Australian  White  925* 

1.45 

1.74 

10 

Horn  926 

21.25 

21.54 

11 

Odessa  927 

20.80 

19.53 

12 

Summit  929 

23.05 

24.03 

13 

Mariout  932 

18.75 

18.15 

14 

Odessa  934 

10.30 

9.84 

15 

Peruvian  935 

22.25 

20.55 

16 

Trebi  936 

30.90 

30.96 

17 

Sandrel  937* 

35.90 

33.48 

18 

Oderbrucker  940 

23.35 

23.79 

19 

Prankish  953 

22.50 

22.05 

20 

Manchuria  956 

30.80 

30.03 

21 

Oderbrucker  957 

29.45 

29.52 

22 

Manchuria  x  Champion  of  Vermont  959 

18.30 

17.49 

23 

Luth  972 

25.05 

26.28 

24 

Red  River  973 

27.25 

28.14 

25 

Featherston  1118 

28.25 

27.00 

26 

Featherston  1119 

25.80 

25.83 

27 

Featherston  1120 

34.35 

35.49 

28 

Hanna  x  Champion  of  Vermont  1121 

13.75 

13.92 

29 

Manchuria  1125 

20.35 

20.94 

30 

Malting  1129 

17.25 

16.44 

Mean 

22.06 

21.95 

Forty  varieties  of  oats  were  compared  in  1919,  but  only  24  of 
these  could  be  replicated  4  times  and  the  remaining  16  were  duplicated. 
The  planting  plan  was  therefore  arranged  as  for  32  varieties,  and 
these  16  varieties  grown  in  two  plots  each  in  place  of  eight  varieties 

th^,v*il^^'*"  V'^^  ^""^   Australian   White   925   were   omitted   from   all   computations   because   of 
theu-  extremely  low   yields,   and   Sandrel  937  because  omitted  in  the  third   series. 


14 


Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 


0^ 

/ 

2 

3 

4 

5 

6 

7 

a 

GK 

9 

/O 

// 

12 

13 

14 

15 

16 

cn 

17 

16 

f9 

zo 

21 

22 

23 

24 

Cf< 

25 

26  27  26 

2$  30 

1 

3, 

n 

32 

cm 

CK 

33 

d^ 

Jl5 

36 

37 

38 

39 

40 

CM 

1 

2 

3 

^ 

5 

6 

7 

8 

Ch 

9 

10 

II 

12 

13 

14- 

15 16  cn  17 

IS 

19 

2021 

22  23  24  CAB 

QY 

17 

18 

IS 

20 

21 

22 

23 

2i 

CK 

26 

26 

27 

2B 

29 

30 

31 

32 

CK 

1 

2 

3 

4 

5 

6 

7 

8 

CH9 

10 

II 

12 

13 

14 

15 

16  CUB 

Ch 

3 

10 

II 

12 

13 

/4 

Id 

16 

OH 

17 

16 

19 

20 

21 

22 

23 

S4 

CK 

33 

34 

35 

36 

37 

38 

39 

4CCfi  1 

2 

3 

-4- 

s 

6 

7 

6 

QiB 

Cfi 

5 

£• 

E 

D 

M 

LI 

L 

T 

1 

P 

L 

/ 

C 

/? 

T 

1 

0 

« 

CKB 

CA 

/ 

8 

3 

i- 

S 

a 

6 

7 

8 

9 

/O 

Ch 

II 

12 

IS 

14 

15 

Cl\ 

/ 

2 

3 

i- 

5 

CK 

6 

7 

8 

9/0 

CK 

II 12 

1314- 

15 

CKb 

CH 

II 

12 

13 

M 

15 

Cl{ 

1 

Z 

3 

f 

J 

cn 

6 

7 

6 

9 

10 

CA 

II 

12 

13 

14 15  Oh 

1 

2 

3 

f 

5 

a 

6 

X 

X 

9 

I0CH3 

Cff 

6 

7 

8 

9 

/O 

Ofl 

II 

12 

13 

/f 

/5 

Cfi 

1 

2 

3 

^ 

5 

C/l 

6 

7 

6 

9 

lOCIill 

12 

13 

I4I5CH 

X 

2 

X 

X 

XCAB 

Figure  3. — Pi,anting  Pi,an  ot  Oats  Variety  and  Strain  Tests  1919. 
Legend:  B,  border.  CK,  check.  Numbers  1-40  in  first  four  ranges,  planting 
numbers  of  oats  varieties,  as  given  in  Table  2.  Numbers  1-15  in  last  three 
ranges,  planting  numbers  of  oats  strains,  as  given  in  Table  3.  X,  test  plots 
planted  to  check  variety  because  of  insufficient  supply  of  seed. 

TabivE  2.— Yields  of  Oats  Varieties. 
In  Bushels  per  Acre.    1919. 


Planting 

Average  yield 

in  interior  rows 

number 

Variety 

Four  series 

Three  series 

1 

A.    Sterilis  nigra 

30.0 

31.7 

2 

Black  Mesdag 

44.2 

44.7 

3 

C.  I.  602 

36.4 

38.1 

4 

C.  I.  603 

53.9 

55.1 

5 

C.  I.  620 

13.1 

14.1 

d 

Early  Champion 

55.5 

53.9 

7 

Early  Gothland 

54.1 

52.8 

8 

Carton  473 

30.6 

31.7 

9 

Carton  585 

21.7 

23.0 

10 

Golden  Giant 

42.0 

44.9 

11 

Irish  Victor 

69.6 

70.2 

12 

Japan  Selection 

47.9 

50.9 

13 

June 

43.1 

44.5 

14 

Kherson  Selection 

67.2 

63.1 

15 

Fulghum  042 

60.9 

57.1 

16 

Lincoln 

51.5 

50.3 

17 

Monarch 

56.0 

53.4 

18 

North  Finnish 

51.0 

49.5 

19 

Scottish  Chief 

59.3 

60.1 

20 

Sparrow  bill  (Missouri) 

39.8 

41.3 

21 

Sparrow  bill  (Cornell) 

42.3 

45.7 

22 

Tobolsk   1 

52.6 

57.3 

23 

Tobolsk  2 

46.1 

51.9 

24 

White  Tartar 

49.7 

50.3 

Mean 

46.6 

47.3 

Experiments  in  Field  Plot  Technic  15 

in  four  plots  each,  as  shown  in  figure  3.  The  rows  were  14  feet  long 
and  were  cut  to  12  feet  in  harvesting.  This  is  a  convenient  size  of 
plot  for  oats  tests  with  10  inches  distance  between  rows,  when  the 
border  rows  are  discarded,  since  the  total  yield  of  three  rows  in 
grams,  divided  by  10,  gives  the  yield  in  bushels  per  acre.  The  oats 
were  planted  at  the  rate  of  10  pecks  per  acre,  on  March  18,  in  rows 
running  north  and  south.  The  season  was  favorable  and  a  good  yield 
of  the  better  varieties  was  obtained.  The  yields  of  the  24  varieties 
replicated  four  times  are  shown  in  Table  2. 

The  oats  strain  test  was  conducted  on  the  same  field,  as  shown  in 
figure  3,  directly  south  of  the  oats  variety  test.  In  planting,  these  two 
tests  were  handled  as  one ;  and  the  rate,  date,  and  method  of  planting 
were  the  same.  The  strains  tested  were  15  strains  of  oats  obtained 
under  the  name  Red  Rustproof  from  various  experiment  stations  and 
seedsmen.  Three  of  these  strains,  0121,  0124,  and  0127,  were  not  true 
to  name,  but  the  remainder  were  taxonomically  Red  Rustproof  oats, 
as  described  by  Etheridge'.  The  oats  strains  were  tested  in  six  series, 
with  check  plots  in  every  sixth  plot.  The  line  of  check  plots  on  the  west, 
however,  gave  abnormally  low  yields,  probably  because  they  were 
located  partly  on  a  dead  furrow  at  the  edge  of  the  experiment  field. 
On  account  of  shortage  of  seed  some  of  the  varieties  could  not  be 
planted  in  the  last  series.    The  first  and  last  series  were  therefore  dis- 

TabIvE  3.— Yields  of  Oats  Strains  (Red  Rustproof). 
In  Bushels  per  Acre.    1919. 


Planting 

Accession 

Average  yield 

number 

number 

3  interior  Rows 

5  Rows 

1 

0119 

49.58      . 

49.41 

2 

0120 

45.83 

44.51 

3 

0121* 

49.43 

53.01 

4 

0122 

47.85 

49.59 

5 

0123 

53.55 

53.47 

6 

0125 

50.18 

49.19 

7 

0126 

44.85 

45.81 

8 

0127* 

38.55 

36.67 

9 

0124* 

63.90 

67.46 

10 

0133 

48.00 

46.49 

11 

0128 

53.55 

53.15 

12 

0129 

49.35 

49.01 

13 

0130 

52.73 

51.89 

14 

0131 

48.60 

47.84 

15 

0132 

55.13 

55.44 

Mean 

50.07 

50.20 

^Not   taxonomically   Red   Rustproof. 


16 


Missouri  Agr.  Exp.  Sta.  Rejsearch  Bulletin  49 


carded.     The  average  yields  of  the  15  strains  in  the  four  remaining 
series  are  shown  in  Table  3. 

Work  of  1920. — ^Wheat  varieties  were  grown  in  5-row  blocks  in 
1919-20.  Ninety-six  varieties  were  included  in  the  test,  four  replica- 
tions being  used.  Fultz  wheat  was  grown  as  a  check  in  every  sixth 
plot.  The  rows  were  18  feet  long  and  were  cut  to  16  feet  in  harvest- 
ing. The  direction  of  the  rows  was  east  and  west.  The  planting  plan 
is  shown  in  figure  1.  The  wheat  was  sown  October  15,  at  the  rate  of 
6  pecks  per  acre.  There  was  considerable  winter  injury  in  the  plots 
and  the  condition  of  the  wheat  in  early  spring  was  rather  poor.  The 
yields  obtained  are  shown  in  Table  4. 

TabIvE  4.— Yields  of  Wheat  Varieties. 
In  Bushels  per  Acre  1920. 


Average  yield 
Planting  3    Interior     5 

number  Variety  Rows     Rows 

1  Beechwood  Hybrid  No.   12..    10.8  11.1 

2  Beechwood  Hybrid  No.   81..    12.8  14.1 

3  Beechwood  Hybrid  No.  85..    12.5  12.7 

4  Beechwood  Hybrid  No.   87..    14.2  13.7 

5  Beechwood  Hybrid  No.  202.   11.9  12.5 

6  Beechwood  Hybrid  No.  207.    13.2  13.6 

7  C.   I.   3808   16.2  16.6 

8  C.   L   3846    14.2  15.6 

9  C.   I.   3972    14.7  15.6 

IOC.  I.   3980   16.4  17.5 

11  C.   L  3988   16.7  17.0 

12  C.    I.    4004    14.3  14.0 

13  Common     Rye     17.3  18.5 

14  Dawson's   Golden  Chaff   13.0  12.3 

15  Deitz     15.1  14.6 

16  Early     Ripe     12.2  12.6 

17  Early  Ripe  No.   26    13.2  14.0 

18  Early    Red    Clawson     9.9  9.5 

19  Farmer's     Friend     18.8  19.9 

20  Fulcaster     14.4  '15u3 

21  Fiiltz     OArxdiias)      12.2  13.0 

22  Gold     Coin     11.7  12.2 

23  Greene    County     15.6  15.1 

24  Harvest    King    No.    7    13.4  14.2 

25  Harvest     Queen     9.6  9.8 

26  Hitkman     ?.8  8l2 

27  mini    Chief    17.5  18.7 

28  Jones     Climax     19. 1  20.7 

29  Kanred     21.0  22.7 

30  Kessinger     ,    18.0  19.3 

31  Kharkov     18.9  20.1 

32  L,eap's     Prolific     14.2  14.8 

33  Mediterranean   No.    8    9.1  9.5 

34  Michigan    Amber    10.7  11.3 

35  Michigan     Amber     (Indiana)   17.0  17.9 

36  Michigan    Amber   No.    7    ...    10.5  10.8 

37  Michigan  Amber  No.   12    . . .     9.3  9.3 

38  Michigan     Wonder     10.9  11.1 

39  Michigan  Wonder  No.  4   ...    12.4  12.7 

40  Michigan  Wonder  No.  8   ...    10.8  11.0 

41  Michigan  Wonder  No.  21    ..     8.2  8.7 

42  Michigan  Wonder  No.  53    ..     8.5  9.6 

43  Michigan  Wonder  No.  54   ..    11.3  10.7 

44  Michigan  Wonder  No.  83    ..    13.6  13.7 

45  Michigan  Wonder  No.  96    ..     9.7  9.7 

46  Michigan  Wonder  No.   103   .     9.7  9.1 

47  Michigan  Wonder  No.   116    .    16.4  15.8 

48  Michigan  Wonder  No.   130   .    14.3  14.2 

49  Michigan  Wonder  No,   140    .    12.3  12.7 


Average  yield 
Planting  3    Interior     5 

number  Variety  Rows     Rows 

50  Michigan  Wonder  No.   141    .    10.7  10.3 

51  Michigan  Wonder  No.    155    .    10.1  9.8 

52  Michigan  Wonder  No.  209   .   12.1  12.5 

53  Michigan  Wonder  No.  211    .     9.9  9.9 

54  Michigan  Wonder  No.  221    .    11.0  11.1 

55  New    York    123-32     17.2  17.5 

56  Niagara     13.8  13.5 

57  Nigger     11.8  11.8 

58  Old    Ironclad    12.5  13.2 

59  Poole    10.5  10.7 

60  Poole   No.   3    11.7  11.0 

61  Poole    B.3     12.5  13.3 

62  Portage   15.9  17.3 

63  Pride    of    Indiana    14.2  14.4 

64  Pride    of    Genessee    15.7  18.1 

65  Reliable     12.6  12.9 

66  Red   Cross    13.1  13.1 

67  Red    May     14.8  14.8 

68  Red    Rock     (Indiana)     18.7  19.7 

69  Red   Rock   (Michigan)    7.5  6.8 

70  Red    Wave     12.9  12.7 

71  Rochester  Red  12.7  12.9 

72  Rosen  Rye  20.7  24.0 

73  S.  P.  I.  11616  10.3  10.9 

74  S.  P.  I.  26012  13.4  12.9 

75  S.  P.  I.  26013  15.2  15.5 

76  S.  P.  I.  26014  17.5  18.8 

77  S.  P.  I,  26015  13.2  13.4 

78  8.  P.  I.  26017  13.4.  13.5 

79  S.  P.  I.  26018  13.6  13.6 

80  S.  P.  I.  26019  11.6  11.6 

81  S.  P.  I.  26022  10.6  10.1 

82  S.  P.  I.  26023  9.1     8.5 

83  S.  P.  I.  26025  12.3  13.1 

84  S.  P.  I.  26029  15,4  15.6 

85  S.  P.  I.  26085  13.2  13.3 

86  Treadwell  12.7  12.8 

87  Valley    12.4  12.1 

88  Velvet  Chaff    No.    2    14.1  12.8 

89  Velvet  Chaff  No.  8 9.0  9.3 

90  Ziegler's    Fly    Proof    10.9  11.7 

91  13D-4a     14.1  13.9 

92  37a-4    14.6  14.7 

93  Fulcaster    (Co-op)    17.4  18.5 

94  Fultz     (Co-op)      15.2  15.9 

95  Kanred    (Co-op)    19.1  20.6 

96  Poole    (Co-op)     19.4  21.0 

Mean    13.4  13.8 


EXPERIME^NTS  IN  FlELD  PlOT  TECHNIC 


17 


to 

w 

H 

w 

pj 

. 

< 

O 

K* 

CJ 

tH 

H 

< 

. 

t4 

(U 

§ 

^ 

tn 

w 

^ 

1 

3 
CQ 

»n 

t-H 

w 

^ 

5 

H 

m  p 


>    M    O 


PU^ 


«  5 

>*    "1 


>   to  O 


u  to 

.si 


11 


IHli^T^t^fo^o0^^.^p^oo^q^>.T^■^ovo■*T^c^^o^o\ooo^u^roT^csJl-^o\^Ocaoo^Ove«nc^ 
l0^uil«o©o6odo6c^iOlOp^fO^O'J-■^liilnf»5vdc^i•^»'>^d•*CS^fOc4uioO^OTt■TH 

^^,-,,-,r-^r^r-l,-lw^,-l,-,^,-^w^r^^^^,-^r^^f^^^T^H,-lrMr^t7-ly-^l-l^,-tT-^<-t^,-l^r^l,-^,-l^,-l^fS^l-*r^*,-tw-i^^^ 


V000O^00^«.»HVOTJ•v0Tt^>,^r50^^0\e0^T^lO0000roOCVIC<I^HT^.-^00^-»^N^0 


lovO■^w^^^H»-^^0^0O^O\c^^00'*>»O«^^0•*^0C^IOvOT^^ee000^<.^0O\^s^O0^ 
TtT^^Cvd^«^odo^o^'oc>\Ofo'*^^"^»olo^"^rou^^ot>I^c<i^^^OT^t.HC^^Oloc^^^^ 


O  O  ,-(  ui  0\  '-• «-! 
fO  ■*  rf  >0  O  i-H  oq 

1^  l-H  rH  «-!  CM  <M  C>J 

d  d  d  o  d  d  d 

•T3  "O  73  XI 13  13 'O    • 

§§§§§§§s  ^ 

OCCCflCCo        g 

C^    Cq    CTl    Cd    CT]     CC    C3  ^^j  r^ 

bobp  bf_b<)  bflbo  Ui"^  vj  ^ 
yooooou>  beta  O 


3t! 

^  3  rt 


^3M 


s     s 


o 

r<^   6 

pqU 


o 
o 

o  . 
AhPh 


ti'O 

8o 

C/3U 


4J^ 

o  o 


dr^.Sg-S^SS 


,^  w^« 


CO    > 


-5   rt   (U 

§  t:  :2  tj  t) -d  73 

P   O   t-   D   0)   (U   « 


oo 

^        CMC. 


,-(  00  JOo«M 

MM   I^'m 


C4  00 


csi 


0»-iC>jroM-«ovOl^OOO\Or;CM*r>'<4-mvOt^OOONOT-iO]tO'*irs 


4^   O      .      .      .     .   «      . 


CM   U 


CO  00 


o  o  o 


.  q  C  3  S  51  <u  «  w.Ji  oSiS^iii 


cvjTj;Tj'0\csi'-;Ofoiooo\inc>flOT^oooooOPO^'*ONO\csiO«n\ovooj»-;^oOM 
^«lo\^-<o^-^^oO"^^o^«I^nvdo^o^o6o^o6Tt^«Iu^o6■^1-^fo■^^»»^dc*j^o^o■^  oxrrjvovOTttnvd'^inoO  odooodo\t^m»«oo 


vOfo^^.^sOc^JfOl>.T^a^u^o^'-^vOT^\oo^^oovooocslOONfovq^>;U^T^^^oq^^lnoqoqlnT-^lovoo^^>^ 

^^OOC>.-^^^^dT^T^»i^»OlOO^o6o6o6o6»0^d^n^s1/ic^^fOr^^OvdfO\d^^T^O^T^^O^ 


)lnT^looo»-^vOTl■c^lotxOt>.tNOO^-;^^OrH^-H»noqoocv^c^^rovo■<^cvIu^c^to»o^«. 


^»^<.O^C^J^O'-*0000^»0\0■*NOOTJ■rHfcOO^OOOCq^-^^^ln^rOC^O\^00^0\»Or-^\0 

voOo^-^.-^^o^<IT^T^vdtl^Tto^o6^>^oo^«I»n^«^\oodTJ■c^I*f^•^^o^CTJ^^opo■^  O'^'vdvoT^iovd'^'vdt^oot^Iodoovd  rtirivo 


!cp^??oS« 


Ooo 

J3     . 


a 
o 
Sn 

et3 


^  fOVO 

o  ►5  o  o  d  d  d  d  d 
oC  c  g  gl  6,o  o  o  o  o  oo  o  o  o 


©►2 


O   rt  rtJ3' 
V,  w  I-  V-  i-o  CQOO 


|SS-<^|<^^^^^^^^^^ 


=  :2     5^h      S 


cS    CO 


(O    2    <«    to    !0    to    (O 


t*>(:Mt;  c 


rtrtrtrtcflcScStflfflrtcflrttflc^ 
bObfit^bobcbcbObobobObobotiflbo 


18  Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 

Work  of  1921. — In  1920-21  ninety-six  varieties  of  wheat 
were  again  tested  by  this  method.  Many  of  the  varieties  were  the  same 
as  those  tested  in  the  preceding  year,  about  20  varieties  being  eliminated 
and  a  corresponding  number  added.  The  planting  plan  was  the  sarae 
as  that  of  the  preceding  season.  Poole  wheat  was  used  as  a  check 
variety.  The  wheat  was  drilled  at  the  rate  of  5  pecks  per  acre,  October 
6,  in  rows  running  east  and  west.  The  season  was  favorable,  but 
yields  were  reduced  by  the  very  rapid  ripening  of  the  wheat  caused  by 
the  hot  dry  weather  in  the  second  and  third  weeks  of  June.  The  yields 
are  shown  in  Table  5. 

Table  6.— Yiei-ds  of  Wheat  Varieties  and  Mixtures 
In  Bushels  per  Acre.    1931. 


Planting 

Average 

yield 

number 

Variety 

3  Interior  Rows 

5  Rows 

1 

Fulcaster 

17.3 

18.6 

2 

Harvest  Queen 

14.3 

14.5 

3 

Mixture  No.  1  (1,  2,  4,  5) 

15.9 

16.2 

4 

Michigan  Wonder 

16.8 

17.8 

5 

Nigger 

10.8 

10.8 

6 

Michigan  Wonder  No.   21 

19.8 

20.8 

7 

Michigan  Wonder  No.  54 

18.9 

19.3 

8 

Mixture  No.  2  (6,  7,  9,  10) 

20.8 

21.3 

9 

Michigan  Wonder  No.  96 

18.5 

18.9 

10 

Michigan  Wonder  No.  209 

21.7 

22.6 

11 

Beechwood  Hybrid  No.  12 

17.4 

18.8 

12 

Beechwood  Hybrid  No.  85 

16.5 

17.3 

13 

Mixture  No.  3  (11,  12,  14,  15) 

17.6 

18.4 

14 

Beechwood  Hybrid  No.  87 

19.9 

19.9 

15 

Beechwood  Hybrid  No.  207 

17.4 

17.9 

16 

Michigan  Wonder  No.  221 

18.6 

20.3 

17 

Kanred 

13.6 

13.8 

18 

Mixture  No.  4  (16,  17,  19,  20) 

17.8 

18.0 

19 

New  York  123-32 

19.6 

19.7 

20 

Red  Rock 

17.6 

17.4 

21 

Red  Hussar 

16.3 

17.8 

22 

Turkey  (Kansas) 

10.8 

10.5 

23 

Mixture  No.  5  (21,  22,  24,  25) 

15.7 

15.9 

24 

Michigan  Amber 

19.2 

19.6 

25 

Nigger 

14.1 

13.4 

26 

Fukaster  (Co-op) 

20.4 

21.2 

27 

Fukaster   (Outl) 

20.1 

20.6 

28 

Mixture  No.  6  (26,  27,  29,  30) 

20.1 

21.0 

29 

Fukaster    (Blazier) 

20.6 

21.5 

30 

Fulcaster  (Cowles) 

20.6 

20.6 

Mean 

17.6 

18.2 

Experiments  in  Fiei^d  Plot  Tt;cHNic 


19 


On  another  field  in  1921,  a  test  of  mixtures  of  varieties  and 
strains  of  wheat  in  comparison  with  their  pure  constituents  was  con- 
ducted. Each  mixture  was  made  up  of  four  varieties  or  strains,  in 
equal  quantities  of  seed  by  weight.  The  composition  of  the  mixtures 
and  the  yields  obtained  are  shown  in  Table  6.  The  planting  plan  is 
shown  in  figure  4.    This  wheat  was  drilled  at  the  rate  of  5  pecks  per 


Cli  I 


Ghee 


27 


28 


29 


30 


Chf6 


n 


Id 


IS 


20 


CHii 


12 


13 


n 


IS 


Cli 


3 


C/(6 


10 


CH 


CKzi 


22 


23 


Z& 


25 


CHie 


17 


18 


IB 


20 


CH 


B 


CH// 


/z 


13 


/4- 


I5C\{ 


/O 


CWae 


27 


28 


29 


30 


CK8/ 


22 


23 


24 


23CKb 


CH 


16 


17 


16 


13 


ZO 


CH// 


/2 


/3 


/^ 


l5C/i 


sC/iee 


27 


28 


29 


30 


as 


CH 


21 


22 


23 


24 


25Cf< 


/6 


/7 


/8 


/$ 


zoCKe 


JO 


CH 


CKB 


CKze 


t7 


ze 


29 


dO 


CHe/ 


ez 


23 


24 


25 


CH// 


/2 


/3 


/4 


75- 


a 


s 


/o 


ChB 


Figure  4.— Pi^anting  Pi,an  of  Wheat  Mixture  Test  1921.  Legend:  B, 
border.  CK,  check.  Numbers  1-30,  planting  numbers  of  varieties  and  mixtures 
tested,  as  given  in  Table  6. 

acre  in  rows  running  north  and  south,  on  October  8,  1920.    This  test 
will  be  referred  to  as  the  wheat  mixture  test. 

In  1921  tests  of  oats  varieties  and  of  oats  strains  were  also  con- 
ducted in  5-row  blocks.  Thirty-two  strains  of  Red  Rustproof,  in- 
cluding many  of  those  tested  in  1919  and  a  number  of  others,  and  32 
strains  of  Kherson  oats,  obtained  in  the  same  way,  were  included  in 
the  oats  strain  test.  The  Kherson  and  Red  Rustproof  strains  were 
arranged  alternately,  and  both  Kherson  and  Red  Rustproof  checks 
were  grown,  as  shown  in  figure  5.  The  test  of  these  64  strains,  in 
four  series,  occupied  16  ranges.  The  next  eight  ranges  on  the  same 
plot  were  used  for  an  oats  variety  test  in  which  32  varieties  of  oats 
were  compared,  each  in  four  replicate  plots.  In  this  part  of  the  field 
the  Kherson  and  Red  Rustproof  check  plots  were  continued.  There 
are  thus  available  the  yields  of  120  plots  each  of  Kherson  and  Red 
Rustproof  oats,  or  five  strips  of  24  plots  of  each  arranged  in  pairs 
side  by  side.  In  both  of  these  experiments  the  rows  ran  east  and 
west,  and  were  18  feet  long,  cut  to  16  feet  in  harvesting.  The  oats 
were  drilled  on  March  12,  at  the  rate  of  10  pecks  per  acre.  The  yields 
of  oats,  particularly  of  the  later-maturing  varieties,  were  materially  re- 
duced by  the  hot  dry  weather  in  the  middle  of  June.  The  yields  of  the 
oats  varieties  are  shown  in  Table  7,  and  those  of  the  strains  in  Table  8. 


20 


Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 


K 


R 


17 


3349 


K 


13 


29 


45  61 


K 


N 


25 


^157 


K 


21 


37 


55K 


B 


/r 


/6 


3/hSO 


K 


14- 


30 


i^ez 


/r 


R 


10 


Z64-2 


S7/r 


/r 


22 


JSSff^ 


B 


n 


/f 


la 


3551 


K 


R 


15 


31 


f7 


63 


/r 


R 


// 


ei 


^35dK 


2339 


55/r 


B 


K 


R 


^Z0d65ZK 


R 


/6 


32 


i66iKR 


12 


26 


ifSoKR 


8 


Zi 


1056KRB 


t\ 


R 


s  2t 


3753 


K 


R 


1733 


4-9 


K 


/3 


29 


4-561 


K 


R 


25  41 


57  n 


RB 


/r 


R 


zz 


38 


54 


K 


R 


f6 


3450M 


/-f 


30 


46 


6Zfi 


/O 


26 


42 


58 


B 


K 


R 


23 


39 


55K 


R 


19 


5551 


K 


R 


1531 


"^76;^ 


K 


R 


// 


27^359 


KR 


B 


/r 


2^ 


^0 


56K 


R 


2036  52 


n 


16 


dZ 


f8 


64K 


R 


fZ 


28 


neo 


n 


B 


K 


Z54-I 


57 


K 


R 


ZI 


J755H 


R 


n 


33 


49 


K 


R 


/J 


zg 


45  61 


H 


R 


B 


n 


R 


70 


ZS'hZ 


58 


K 


R 


ZZ 


38 


54 


R 


f8 


34-50 


n 


14- 


30 


4^ 


62 


K 


3 


KR 


7/27^3 


59 


KR 


23 


3955  K 


J9 


3551 


K 


15 


31 


47 


63 


K 


R 


B 


K 


R 


12  28 


f460 


K 


R 


8 


24 


4056K 


20  36 


52 


K 


R 


16 


32 


^8 


6f 


/r 


R 


B 


KR 


13 


29i66l 


K 


R 


25^^151^ 


R 


21 


3753 


K 


R 


77 


33 


i3 


K 


B 


K 


R 


/^30i-662K 


R 


10  e  6 


^256  7\ 


R 


21 


3854K 


R 


16 


34 


SO 


71 


R 


5 


K 


R 


15  dt 


"tred 


K 


R 


II 


27 


43 


59 


7i 


R 


23 


3955KR 


19 


35  5 J 


/r 


3 


K 


R 


16 


52 


46 


64  H 


R 


12 


2S 


44 


60 


K 


R 


24 


4056 


K 


R 


20  36 


52 


K 


B 


K 


65 


7361 


89 


K 


R 


71 


79 


d795R 


R 


69 


77 


85 


93 


K 


R 


61 


7563 


91 


K 


R 


B 


K 


R 


66 


74  62  90  K 


R 


72 


803896  K 


R 


70 


7866 


94 


K 


R 


66 


76S4 


ez 


K 


B 


K 


R 


67 


758391 


K 


R 


65 


7381 


63 


K 


71 


73  8735  K 


69 


778593 


n 


R 


K 


R 


6876 


8-^92 


KR 


66 


74 


6290 


n 


n 


72 


806696 


K 


R 


70 


78  66 


94 


/r/f 


B 


K 


R  6977  8593  K 


R 


67 


755391 


n 


R 


65  73 


8169 


/r 


R 


71 


79d795/f  R 


B 


K 


70 


78 


6694 


KR 


68 


768492 


n 


R 


66 


74 


92 


90 


K 


R 


72 


806836 


K 


B 


K 


R 


71 


798795K 


R 


69 


778693 


ftRsi 


7563 


91 


K 


R 


65  738189 


K 


RB 


K 


R 


72WBS96 


K 


R 


70 


768694 


/r 


68 


7684 


92 


K 


66  74 


d290H 


B 


Figure  5.— Planting  Plan  of  Oats  Variety  and  Strain  Tests  1931. 
Legend:  B,  border.  K,  Kherson  check.  R,  Red  Rustproof  check.  Numbers 
1-64,  planting  numbers  of  oats  strains,  as  given  in  Table  8.  Numbers  65-96, 
planting  numbers  of  oats  varieties,  as  given  in  Table  7. 


Experiments  in  Fi^ld  P1.0T  Technic  21 


Tabi,e  7.— Yields  oe  Oats  Varieties. 
In  Bushels  per  Acre.    1921. 

Planting  Average  yield 

number  Variety  3  Interior  Rows      5  Rows 


65 

Burt 

66 

Canadian 

67 

C.  I.  603 

68 

Culberson 

69 

Danish  Island 

70 

Early  Dakota 

71 

Early  Gothland 

72 

Carton  748 

73 

Green  Russian 

74 

Irish  Victor 

75 

Joanette 

76 

Fulghum  042 

77 

Monarch 

78 

Monarch  Selection 

79 

Scottish  Chief 

80 

Silvermine  050 

81 

Silvermine  Selection 

82 

Sparrowbill   (C) 

83 

Sterilis  Selection 

84 

Storm  King 

85 

Swedish  Select  057 

86 

Fulghum  065 

87 

Fulghum  0113 

88 

Silvermine  0115 

89 

Silvermine  0117 

90 

Fulghum  0124 

91 

Fulghum  0145 

93 

Fulghum  0149 

93 

Fulghum   0151 

94 

Fulghum  0152 

95 

Silvermine  0165 

96 

Swedish  Select  0165 

Mean 

49.13 

51.94 

25.31 

25.13 

22.50 

23.06 

24.75 

25.13 

19.69 

19.13 

21.56 

21.56 

23.44 

22.13 

21.00 

20.81 

26.06 

26.25 

29.81 

32.06 

19.31 

19.69 

45.19 

47.44 

29.63 

31.88 

35.63 

36.38 

26.63 

27.38 

31.69 

32.06 

22.13 

24.94 

15.38 

14.63 

38.63 

36.94 

20.06 

17.63 

21.00 

19.50 

42.00 

44.81 

42.00 

45.38 

25.13 

24.94 

21.75 

22.69 

45.38 

48.38 

39.19 

41.81 

42.75 

47.06 

39.75 

4j3.88 

39.75 

42.38 

28.31 

26.81 

20.81 

18.56 

29.85 

30.70 

22 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


Table  8. — Yields  of  Oats  Strains  (Red  Rustproof  and  Kherson). 
In  Bushels  per  Acre.    1921. 


Red  Rustproof  strains 

Kherson  strains 

Average 

yields 

Average  yields 

Planting 

3  Interior 

5 

Planting 

3  Interior 

5 

number 

Strain 

Rows 

Rows 

Number 

Strain 

Rows 

Rows 

1 

066 

24.00 

23.25 

2 

023 

35.25 

36.38 

3 

067 

24.00 

21.75 

4 

040 

36.57 

37.50 

5 

068 

23.25 

23.44 

6 

041 

36.56 

38.81 

7 

069 

19.31 

18.00 

8 

052 

38.06 

38.81 

9 

072 

18.38 

18.75 

10 

053 

39.75 

42.00 

11 

074 

22.31 

20.63 

12 

079 

32.63 

34.88 

13 

075 

24.19 

22.13 

14 

080 

35.44 

38.25 

15 

0118 

16.50 

16.31 

16 

082 

40.88 

41.44 

18 

0119 

22.31 

21.38 

17 

083 

35:44 

38.25 

20 

0120 

21.19 

19.69 

19 

085 

38.25 

41.81 

22 

0122 

19.13 

17.81 

21 

086 

36.75 

37.69 

24 

0125 

21.00 

19.88 

23    Mixture** 

33.75 

36.38 

26 

0126 

25.31 

22.50 

25 

088*** 

27.00 

27.56 

28 

0128 

20.44 

20.25 

27 

089 

30.94 

31.69 

30 

0129 

21.94 

21.56 

29 

090 

36.38 

38.06 

32 

0130 

21.75 

20.25 

31 

091 

30.19 

31.88 

33 

0131 

24.56 

23.25 

34 

094 

31.69 

33.56 

35 

0132 

17.63 

19.13 

36 

095 

38.81 

39.75 

37 

0133 

18.94 

18.75 

38 

096 

36.38 

38.06 

39 

0134 

16.50 

15.75 

40 

097 

31.31 

32.25 

41 

0135 

17.63 

15.65 

42 

098 

38.63 

39.19 

43 

0136* 

32.44 

33.19 

44 

099 

38.81 

38.25 

45 

0141 

21.94 

21.19 

46 

0100 

40.13 

42.75 

47 

0163 

13.88 

12.94 

48 

0155 

37.50 

38.63 

50 

0169 

15.38 

14.44 

49 

0157 

43.69 

45.00 

52 

0181 

19.88 

18.00 

51. 

0158 

34.69 

35.25 

54 

0182 

19.88 

19.13 

53 

0159 

33.38 

33.94 

56 

0183* 

41.44 

43.31 

55 

0160 

30.19 

31.13 

58 

0383 

23.63 

24.00 

57 

0161 

34.69 

36.00 

60 

0391 

29.44 

30.19 

59 

0162 

25.31 

25.69 

62 

0394 

22.31 

21.66 

61 

0167 

40.69 

39.94 

64 

0395 

23.25 

21.94 

63 

0174 

36.75 

38.25 

Mean 

21.00 

20.12 

Mean 

35.79 

37.14 

♦Not  taxonomically  Red  Rustproof.  Ex- 

**Mixture 

of    strains 

082,    094, 

0100, 

cluded 

from  average. 

0174. 

***Not   taxonomically   Kherson. 

Ex. 

eluded  from  average. 

Experiments  in  Field  Plot  Technic  23 

COMPETITION  AS  A  SOURCE  OF  ERROR  IN  PRELIMINARY 

TESTS. 

Previous  Investigation. — The  possibility  of  error  from  competi- 
tion in  single-row  tests  was  noted  by  Montgomery"  in  1913,  in  the 
following  passage : 

"In  1908  it  was  observed  that  a  certain  strain  of  early  wheat  in  a  series 
of  row  plats  made  a  very  poor  appearance  at  harvest  time,  while  the  same 
strain  planted  in  centgeners  made  a  much  better  comparative  showing.  Ap- 
parently the  larger  and  faster  growing  strains  on  each  side,  the  rows  being 
only  8  inches  apart,  exercised  some  competitive  effect.  This  effect  of  com- 
petition has  been  noted  for  two  years  since.  Also  in  certain  variety  tests 
of  oats,  grown  in  row  plats  10  inches  apart,  the  same  effect  was  noted. 
Exact  data  cannot  be  given  on  this  point,  as  the  results  from  the  series  of 
plats  planted  in  1909  and  in  1910  for  this  purpose  were  seriously  impaired 
by  unfavorable  conditions;  but  Table  XVIII,  giving  results  from  adjacent 
row  plats  sown  at  different  rates,^  shows  that  the  800-seed  rate  made  a  marked 
increase  over  the  700-seed  rate,  while  in  a  similar  series  of  blocks  (Table 
XIX),  sown  at  the  same  rate,  this  marked  increase  was  not  noted.  Since  the 
800-seed  row  was  always  adjacent  to  the  400-seed  row,  it  may  have  had  some 
advantage  on  this  account.  Danger  from  this  source  can  probably  be  avoided 
if  care  is  taken  to  plant  only  similar  varieties  in  adjacent  rows.  Where  the 
block  plat  is  used  this  source  of  error  is  eliminated." 

Hayes  &  Arny*  found  considerable  competition  between  rod-rows 
grown  one  foot  apart.  Three-row  plots  were  used  in  variety  tests  of 
winter  wheat,  spring  wheat,  barley,  and  oats,  and  the  yields  of  each 
row  determined  separately,  in  1916.  The  comparative  yield  of  the 
border  rows  in  each  plot  was  then  correlated  with  the  comparative 
height  and  yield  of  the  adjacent  rows.  There  was  some  effect  on  the 
yield  of  border  rows  due  to  the  height  of  adjacent  rows  in  the  case 
of  barley  and  winter  wheat.  The  results  were  variable  in  different 
plots.  In  the  case  of  oats  the  effect  of  height  was  rather  obscure,  and 
in  the  case  of  spring  wheat  it  was  not  apparent.  The  yield  of  adjacent 
rows  appeared  to  be  of  some  importance  in  the  barley  tests  and  in 
some  of  the  spring  wheat  tests.  These  results  led  to  the  adoption  of 
3-row  plots  with  discarded  border  rows  for  preliminary  testing  at 
the  Minnesota  Station. 

Love  and  Craig*  in  describing  the  methods  used  in  cereal  investiga- 
tions at  the  Cornell  Station  describe  the  single-row  test  and  add :  "In 
order  to  prevent  any  effect  which  may  be  caused  by  two  unlike  sorts 
growing  together  the  different  strains  are  arranged  according  to 
earliness  and  other  characters  so  as  to  reduce  this  source  of  error  to  a 
minimum.*' 


24 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


Kiesselbach"' '  has  published  rather  extensive  data  on  the  compe- 
tition between  adjacent  rod-rows.  In  his  experiments  the  crops  were 
compared  in  alternating  single-row  plots  and  in  alternating  5-row 
blocks,  each  replicated  fifty  times.  In  some  cases  the  border  rows  of 
5-row  plots  were  discarded.  The  deviation  of  the  result  in  the  test 
in  single-row  plots  from  that  of  the  test  in  5-row  plots  is  regarded  as  the 
measure  of  the  effect  of  competition.  The  comparative  yields  of  va- 
rieties of  wheat  and  oats  in  alternating  single  rows  and  in  alternating 
5-row  plots  are  shown  in  Table  9,  from  Kiesselbach\ 


Tabids  9. — Relative  Yiei^ds  of  Two  Smai^i,  Grain  Varieties  When  Compared 
IN  Alternating  Rows  and  in  Ai^ternating  5-Row  PivATs  (Kiesselbach). 


Wheat 

Oats 

Average  yield  of 

50   plats 

Average  yield  of  50  plats 

Year  and 

Alternating 

Alternating 

Year  and 

Alternating 

Alternating 

variety 

single  rows 

5-row  blocks* 

Variety 

single  rows 

5-row  blocks* 

% 

% 

% 

% 

1913 

1913 

Turkey 

100 

100 

Kherson 

100 

100 

Big  Frame 

107 

97 

Burt 

130 

112 

1914 

1914 

Turkey 

100 

100 

Kherson 

100 

100 

Big  Frame 

85 

97 

Burt 

139 

101 

1913 

1913 

Turkey 

100 

100 

Kherson 

100 

100 

Neb.  No. 

107 

107 

Swedish 

82 

77 

28 

Select 

1914 

1914 

Turkey 

100 

100 

Kherson 

100 

100 

Neb.  No. 

63 

85 

Swedish 

89 

93 

28 

Select 

♦Yield  based  on  3  inner  rows  of  5-row  plats  in  1914. 

Kiesselbach  also  submits  interesting  data  on  the  competition  of 
pure  line  selections  of  the  same  variety.  It  might  be  supposed  that 
such  strains,  being  similar  in  varietal  characteristics,  would  be  little 
affected  by  competition,  and  could  therefore  be  safely  compared  in 
single-row  plots.  The  average  relative  yields  of  three  strains  of  Turkey 
wheat  in  single  rows  and  in  blocks  for  two  seasons,  however,  showed 
that  the  two  better  strains  were  favored  approximately  20  per  cent  and 
15  per  cent,  respectively,  at  the  expense  of  the  poorer  strain,  in  the 
single-row  test.  A  strain  which  yielded  26  per  cent  mor,e  than  an- 
other in  the  single-row  test  yielded  only  6  per  cent  more  in  the  block 


Experiments  in  Field  Plot  Technic  25 

test.  Kiesselbach  has  therefore  adopted  the  practice  of  testing  such 
strains  in  5-row  blocks  repHcated  ten  times  instead  of  in  single-row 
plots. 

Love'  has  criticized  these  results  because  in  some  cases  at  least 
the  rows  ran  east  and  west  rather  than  north  and  south.  He  states 
that  in  experiments  at  Ithaca,  New  York,  there  is  little  competition  be- 
tween varieties  grown  in  single  rows,  when  the  rows  run  north  and 
south.  "In  order  to  obviate  any  criticism  of  this  method,"  he  adds,  "it 
might  be  well  to  follow  the  plan  of  arranging  varieties  so  that  late 
sorts  are  grown  together  and  the  earlier  ones  together.  In  other  words, 
the  different  sorts  could  be  so  arranged  that  they  grade  into  one  another 
as  regards  yield,  earliness,  and  the  Hke."  To  this  Kiesselbach'  replies 
that  in  some  of  his  competition  studies  the  rows  ran  north  and  south 
and  in  others  east  and  west,  and  that  striking  competition  occurred  in 
both  cases.  He  adds  that  although  error  resulting  from  row  compe- 
tition would  undoubtedly  be  reduced  by  grouping  varieties  of  sim- 
ilar growth  habits  together,  it  appears  that  varieties  fairly  similar 
in  growth  habit  may  vary  for  some  reason  in  relative  competitive  qual- 
ity. 

Experimental  Results. — Some  further  evidence  on  competition 
as  a  source  of  error  in  plot  experiments  is  afforded  by  a  study  of  the 
relative  yields  of  border  rows  and  interior  rows  in  the  5-row  blocks  used 
in  these  preliminary  tests.  It  should  be  remembered,  of  course,  that  the 
effect  on  yield  would  be  decidedly  greater  in  single  rows  exposed  to  com- 
petition on  both  sides  than  in  these  border  rows,  which  compete  with 
another  sort  on  only  one  side.  The  extent  of  the  error  from  compe- 
tition in  such  border  rows  is  of  interest  in  determining  whether  it  is 
necessary  to  discard  the  border  rows  of  small  blocks.  When  5-row 
blocks  are  used,  even  if  the  border  rows  are  not  discarded,  the  relative 
effect  of  competition  is  greatly  reduced,  since  only  two  of  the  five 
rows  are  subject  to  varietal  competition  and  these  are  exposed  only 
on  one  side.  If  this  results  in  reducing  the  error  from  competition  to 
a  low  point,  or  if  varieties  can  be  so  arranged  as  to  give  this  result, 
it  may  be  advisable  in  practice  to  harvest  5-row  blocks  entire,  thus 
avoiding  the  principal  objection  to  the  use  of  border  rows — ^the  loss  of 
a  considerable  portion  of  the  experimental  area. 

Competition  is  particularly  important  as  a  source  of  error  because 
of  the  fact  that  it  tends  to  affect  replicate  plots  similarly,  and  conse- 
quently does  not  necessarily  increase  plot  variability.  For  this  reason 
it  is  likely  to  escape  detection,  and,  when  it  is  involved  in  an  experi- 
ment, its  effect  cannot  be  measured.  Ther,e  is  no  'great  objection  to  a 
considerable  experimental  error  from  plot  variability  in  field  experi- 


26 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


ments,  if  the  experimenter  determines  the  extent  of  the  error  and  draws 
his  conclusions  accordin'gly.  But  a  pr,eliminary  variety  test  in  which 
error  from  competition  is  not  controlled  may  be  very  nearly  worthless 
as  an  indication  of  the  relative  value  of  varieties  for  field  conditions, 
because  actually  the  relative  values  of  the  varieties  tested  may  frequent- 
ly differ  by  50  or  100  per  cent  from  the  values  determined  in 
the  test,  without  the  slightest  indication  in  the  experimental  results. 

Illustrations  of  Eifects  of  Compe^iition. — The  error  from  competi- 
tion may  be  illustrated  by  numerous  examples  from  each  of  the  eight 
tests  here  reported.  An  extreme  case  is  the  effect  of  competition  on 
the  relative  yield  of  wheat  and  rye.  Two  varieties  of  rye,  common 
rye  and  Rosen  rye,  were  included  in  the  wheat  variety  test,  for  com- 
parison with  wheat.  The  average  yields  of  Rosen  rye  and  of  the  va- 
rieties of  wheat  adjoining  it  on  either  side,  in  interior  rows  and  com- 
peting border  rows  of  the  four  series,  were  as  follows : 


Yield  in 

Yield  in  competing 

Season          Variety 

interior 

rows 

border 

rows 

Bushels 

Relative 

Bushels 

Relative 

Niagara    (Wheat) 

13.8 

67 

10.0 
r30.4 

33 
100 

1920. 

Rosen  (Rye) 

20.7 

100 

[27.7 

100 

Velvet  Chaff  No.  2   (Wheat 

14.1 

68 

9.8 

35 

Red    Hussar    (Wheat) 

14.3 

80 

11.6 
[19.7 

59 
100 

1921. 

Rosen   (Rye) 

17.9 

100 

25.4 

100 

Poole  (ck)   (Wheat) 

11.8 

66 

11.2 

44 

The  disturbance  of  the  true  comparative  value  of  the  varieties 
by  competition  may  be  determined  by  comparing  their  relative  yields 
in  interior  rows  and  in  border  rows.  Thus  Niagara  wheat  in  1920 
yielded  67  per  cent  as  much  as  Rosen  rye  in  plots  protected  from  com- 
petition, but  only  33  per  cent  as  much  in  rows  not  protected  from 
competition.  Similarly  the  yield  of  Velvet  Chaff  No.  2  wheat  was  re- 
duced from  68  per  cent  to  35  per  cent  by  competition  with  Rosen  rye. 
In  the  following  season  the  reduction  in  yield  of  the  two  varieties  of 
wheat  adjoining  Rosen  rye  (Red  Hussar  and  Poole)  was  not  so 
great,  but  was  still  decidedly  significant.     This  clear  case  of  compe- 


Experiments  in  Field  Plot  Teciinic 


27 


tition  serves  to  illustrate  the  phenomenen,  although  the  competition 
between  wheat  and  rye  has  little  significance  in  itself  as  regards  va- 
riety tests  in  general,  since  wheat  and  rye  are  not  commonly  included 
in  the  same  test. 

Ordinarily  the  competition  between  varieties  of  the  same  crop 
is  not  so  extreme.  There  are,  however,  a  number  of  cases  in  which 
a  variety  of  wheat  or  oats  profited  almost  as  extremely  in  competition 
with  other  varieties  of  the  same  crop  as  did  the  rye  in  competition 
with  wheat  in  the  cases  cited  above.  The  wheat  variety,  Michigan 
Wonder  No.  116,  which  grew  between  two  other  wheat  varieties, 
Leap's  Prolific  and  Poole  Selection,  in  1921,  gave  the  following  results, 
as  an  average  of  the  four  series: 


Variety 

Yield  in 
interior  rows 

Yield  in  competing 
border  rows 

Bushels 

Relative 

Bushels 

Relative 

Leap's  Prolific 

Michigan  Wonder  No.  116 

Poole    Selection 

14.9 
16.4 
15.3 

91 

100 

93 

9.9 
ri8.8 

[21.7 
11.5 

53 
100 

100 
53 

The  efifect  of  competition  in  this  case  is  almost  as  pronounced 
as  in  the  case  of  the  rye,  although  the  three  wheat  varieties  concerned, 
when  protected  from  competition,  gave  almost  equal  yields  and  differed 
little  in  date  of  heading,  date  of  maturity,  and  height.  In  this  case 
a  small  difference  in  actual  value  between  the  varieties,  as  indicated 
by  their  yields  when  protected  from  competition,  is  greatly  increased 
when  their  yields  in  adjacent  single  rows  are  compared. 

A  striking  case  of  competition  in  the  oats  variety  test  of  1921  was 
that  of  the  three  varieties  Sterilis  Selection,  Fulghum,  and  Kherson, 
the  check  variety.     Their  average  yields   were  as   follows: 


Yield  in 

Yield  in  competing 

Variety 

interior  rows 

border  rows 

Bushels 

Relative 

Bushels 

Relative 

Sterilis  Selection 

38.63 

99 

28.50 
["48.75 

58 
100 

Fulghum 

39.19 

100 

1  42.94 

100 

Kherson    (check) 

40.69 

104 

34.18 

70 

28 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


These  three  varieties,  which  gave  almost  equal  yields  in  rows 
protected  from  competition,  differed  decidedly  in  their  yields  in  ad- 
jacent rows.  Although  Kherson  outyielded  Fulghum  4  per  cent  in 
plots  protected  from  competition,  its  yield  was  30  per  cent  less  than 
that  of  Fulghum  in  single  rows  not  protected  from  competition. 

Extreme  effects  of  competition  were  shown  in  very  numerous 
cases  in  the  tests  of  Kherson  and  Red  Rustproof  strains  in  1921.  An 
example  from  this  plot  is  the  following: 


Strain 

Yield  in 
interior  rows 

Yield  in  competing 
border  rows 

Bushels 

Relative 

Bushels 

Relative 

0169  (Red  Rustproof  check) 
067   (Red  Rustproof) 
085  (Kherson) 

18.38 
24.00 
38.25 

77 
100 
159 

22.31 
ri8.75 

[17.44 
51.94 

119 
100 

100 
298 

The  extreme  advantage  of  the  Kherson  strain  in  competition  with 
the  Red  Rustproof,  increasing  its  margin  of  superiority  from  59  per 
cent  to  198  per  cent,  is  particularly  striking.  Probably  even  more 
significant  is  the  effect  of  competition  between  the  two  Red  Rustproof 
strains,  resulting  in  the  conversion  of  a  23  per  cent  loss  to  a  19  per 
cent  gain. 

All  of  the  cases  cited  above  are  taken  from  plots  in  which  the 
rows  ran  east  and  west.  Some  examples  of  varietal  competition  from 
tests  in  rows  running  north  and  south  are  the  following: 

In  the  barley  variety  test,  the  variety  Featherston  1118  occurred 
between  Red  River  973  and  Oderbrucker  (the  check  variety).  The 
average  yields  of  these  three  varieties  in  the  three  series  were  as  follows : 


Variety 

Yield  in 
interior  rows 

Yield  in  competing 
border  rows 

Bushels 

Relative 

Bushels 

Relative 

Red   River  973 
Featherston  1118 
Oderbrucker    (ck) 

27.25 
28.26 
34.87 

96 
100 
123 

31.20 
["24.60 

[25.65 
42.19 

127 
100 

100 
164 

Experiments  in  FieivD  Plot  Technic 


29 


In  this  case  the  advantage  of  Oderbrucker  over  Featherston  was 
almost  tripled  by  competition,  and  Red  River,  which  yielded  less  than 
Featherston  in  the  interior  rows,  excelled  it  materially  in  yield  in  the 
border  rows. 

The  oats  varieties  tested  in  rows  running  north  and  south  in  1919 
showed  marked  effects  of  competition  in  several  cases.  The  follow- 
ing will  serve  as  an  example ; 


Yield  in 

Yield  in  competing 

Variety 

interior  rows 

border  rows 

Bushels 

Relative 

Bushels 

Relative 

Kherson  Selection 

61.3 

111 

84.7 
'49.4 

171 
100 

Fulghum  042 

57.1 

100 

50.7 

100 

Lincoln 

50.3 

88 

57.5 

113 

In  this  case  Lincoln,  yielding  12  per  cent  less  than  Fulghum  in  in- 
terior rows,  yielded  13  per  cent  more  than  Fulghum  in  border  rows; 
while  the  advantage  of  Kherson  Selection  over  Fulghum  was  in- 
creased from  11  per  cent  to  71  per  cent. 

Marked  competition  is  hardly  to  be  expected  in  the  oats  strain  test 
of  1919,  regardless  of  the  direction  of  the  rows,  because  of  the  sim- 
ilarity of  the  strains  in  varietal  characters.  Three  strains  which  proved 
to  be  taxonomically  unlike  Red  Rustproof  were  included  in  this  test, 
and  each  of  these  shows  clearly  the  effects  of  competition.  For  ex- 
ample, strain  0124,  which  was  classified  as  Fulghum,  gave  the  follow- 
ing yields  in  comparison  with  the  adjoining  strains,  0127,  classified  as 
Kherson,  and  0133,  classified  as  Red  Rustproof : 


Strain 

Yield  in 
interior  rows 

Yield  in  competing 
border  rows 

Bushels 

Relative 

Bushels 

Relative 

01J27  (Kherson) 
0124  (Fulghum) 
0133   (Red    Rustproof) 

38.55 
63.90 
48.00 

60 

300 

75 

32.40 
'66.83 

[78.75 
43.20 

48 
100 

100 
55 

30 


Missouri  Agr.  Exp.  Sta.  Rksearch  Bulletin  49 


Moreover,  the  Red  Rustproof  strains  showed  competitive  effects 
among  themselves  to  some  extent,  though  not  so  conspicuously  as  dif- 
ferent varieties.  For  example  the  strains  0122  and  0123,  which  were 
taxonomically  identical,  yielded  as  follows: 


Strain 

Yield  in 
interior  rows 

Yield  in  competing 
border  rows 

Bushels 

Relative 

Bushels 

Relative 

0122  (Red   Rustproof) 

0123  (Red  Rustproof) 

47.85 
53.55 

89 
lOO 

55.13 
49.28 

112 
100 

Strain  0122  which  was  apparently  11  per  cent  inferior  to  strain 
0123  in  the  yields  of  interior  rows,  appeared  to  be  12  per  cent  superior 
to  the  same  strain  in  the  yields  of  their  adjacent  border  rows. 

In  the  wheat  mixture  test  of  1920  also  the  rows  ran  north  and 
south.    An  example  of  competition  from  this  test  is  the  following : 


Yield  in 

Yield  in  competing 

Variety 

interior  rows 

border  rows 

Bushels 

Relative 

Bushels 

Relative 

Poole  (check) 

15.1 

81 

14.5 
r24.2 

60 
100 

Michigan  Wonder   No.   221 

18.6 

100 

[21.4 

100 

Kanred 

13.6 

73 

12.5 

58 

In  this  case  also  differences  in  yield  were  increased  by  compe- 
tition. 

The  individual  cases  cited  above  will  serve  to  show  the  existence 
of  competition  as  a  source  of  error  in  these  tests.  As  a  result  of 
competition  the  differences  between  varieties  may  be  increased  or  de- 
creased, and  in  some  cases  a  material  advantage  in  yield  may  be  con- 
verted to  a  material  disadvantage.  The  phenomenon  occurs,  under 
conditions  at  Columbia,  whether  the  rows  run  north  and  south  or 
east  and  west.  Of  course  it  is  not  true  that  all  of  the  difference  in 
yield  between  border  rows  and  interior  rows  is  necessarily  caused 
by  varietal  competition.  Some  variation  in  the  yield  of  adjacent  rod- 
rows  will  occur  regardless  of  competition.    When  the  means  of  only 


Experiments  in  Field  Plot  Technic  31 

four  determinations  are  compared  the  effect  of  this  variability  may  be 
considerable.  If  a  field  uniformly  seeded  to  a  single  strain  were  har- 
vested in  rod-rows  and  assumed  to  be  made  up  of  several  different 
varieties  each  in  four  distributed  plots,  doubtless  the  average  border 
yield  would  differ  materially  from  the  average  interior  yield  in  several 
"varieties."  It  is  not  however,  likely,  that  such  differences  as  those 
cited  above  would  be  caused  by  chance  variability.  Nevertheless,  no 
final  conclusions  regarding  competition  as  a  source  of  error  should  be 
drawn  from  such  individual  cases.  The  extent  of  error  from  compe- 
tition is  better  shown  in  the  average  differences  between  border  yields 
and  interior  yields,  and  in  the  mean  coefficients  of  competition  for 
complete  tests.    They  are  given  in  the  next  section. 

Relation  of  Competition  to  Various  Characteristics  of  the  Com- 
peting Varieties. — It  is  essential  that  competition  be  eliminated  by  the 
use  of  border  rows,  or  counteracted  by  some  such  means  as  grouping 
varieties.  The  latter  is  decidedly  the  preferable  method,  from  the 
standpoint  of  economy,  if  satisfactory  results  may  be  obtained  by  its 
use.  But  competition  cannot  be  effectively  controlled  by  grouping 
varieties  unless  there  is  a  close  correlation  between  competitive  value 
and  some  character  Hke  earliness  or  height,  which  may  be  known  in 
advance.  Determinations  of  the  correlation  between  competitive  ef- 
fects and  various  characteristics  of  the  varieties  have  therefore  been 
made  for  each  of  the  tests.  The  preliminary  determinations  were  made 
as  follows: 

(1)  The  average  yield  in  interior  rows  and  the  average  yield 
in  the  border  rows  on  each  side  for  all  replicate  plots  of  each  variety 
or  strain  was  determined.  The  replicate  plots  thus  averaged  were 
grown  between  the  same  varieties  in  each  series,  and  it  may  be  assumed 
therefore  that  their  border  rows  were  subject  to  the  same  competition. 
In  the  following  discussion  of  competition  each  individual  case  repre- 
sents the  mean  of  all  the  replicate  plots  of  the  test  in  question.  For 
example,  when  it  is  stated  that  the  correlation  between  competition 
and  yield  is  determined  in  a  test  in  which  one  hundred  cases  of  compe- 
tition are  involved,  each  of  the  hundred  cases  represents  the  mean  of 
three  or  four  determinations  in  replicate  plots.  In  most  cases  the 
number  of  replicate  plots  was  four.  In  the  barley  test  of  1919  only 
three  series  were  grown,  and  in  the  oats  variety  test  of  1919,  though 
four  series  were  grown,  only  three  could  be  used  because  one  border 
row  of  each  variety  in  the  first  series  was  harvested  for  seed  and 
laboratory  material. 

(2)  Corresponding  average  yields  were  determined  for  check 
plots,  those  adjoining  the  same  variety  being  averaged  together.    For 


32  Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 

example,  in  the  wheat  variety  test  diagrammed  in  figure  1  the  four 
check  plots  which  adjoined  variety  1  (one  in  each  series)  were  aver- 
aged together,  the  four  adjoining  variety  2,  the  four  adjoining  variety 
3,  etc.  The  four  check  plots  adjoining  varieties  89,  90,  91,  etc.  were 
similarly  averaged. 

(3)  The  average  yield  of  each  border  row  for  each  variety  was 
converted  to  the  percentage  of  the  average  yield  of  the  same  variety 
in  its  interior  rows.  These  yields  of  border  rows  in  percentage  will 
be  referred  to  as  "relative  border  yields."  The  relative  border  yield 
gives  a  rough  indication  of  the  effect  of  competition  on  the  variety. 
When  it  is  above  100,  the  variety  yielded  more  in  border  rows  (subject 
to  competition)  that  in  interior  rows  (protected  from  competition). 
When  it  is  below  100,  the  border  yield  was  less  than  the  interior  yield, 
in  proportion. 

(4)  An  approximate  measure  of  the  competition  between  each 
pair  of  adjacent  varieties  was  obtained  by  dividing  the  higher  relative 
border  yield  by  the  lower,  in  the  case  of  their  adjacent  border  rows, 
and  substracting  100  from  the  result.  When  the  variety  on  the  left 
has  a  higher  relative  border  yield,  this  is  given  a  positive  sign;  in  the 
reverse  case  a  negative  sign.  This  figure  is  simply  the  predominance 
of  the  more  strongly  competing  variety  over  the  other  in  percentage  of 
relative  border  yield.  It  will  be  referred  to,  for  convenience,  as  the 
coefficient  of  competition. 

(5)  This  measure  of  competition  was  correlated  with  various 
characteristics  of  the  competing  varieties,  including  the  relative  yields 
in  interior  rows,  the  relative  grain-straw  ratios,  the  relative  dates  of 
heading  and  of  maturity,  and  the  relative  heights.  In  correlating  com- 
petition with  the  relative  yield  of  the  interior  rows,  the  relative  yield 
was  determined  by  dividing  the  higher  yield  by  the  lower,  subtracting 
100,  and  assigning  a  positive  or  negative  sign,  as  before.  The  correla- 
tion determined,  therefore,  is  the  correlation  between  the  percentage 
advantage  of  one  variety  over  another  in  competition,  and  the  differ- 
ence in  yield  of  the  two  varieties,  expressed  in  percentage,  when  pro- 
tected from  competition.  Relative  grain-straw  ratios  were  determined 
similarly,  the  ratios  being  first  obtained  by  dividing  the  yield  of  straw 
by  the  yield  of  grain.  Relative  dates  of  heading  and  maturity  and 
relative  heights  were  determined  simply  by  subtracting  the  value  for 
one  variety  from  the  value  for  the  other.  In  each  case,  of  course,  the 
sign  was  determined  in  the  same  way. 

A  simple  example  explained  in  detail  may  serve  to  make  this 
method  clear.  In  the  wheat  variety  test  of  1921  the  varieties  Fultz 
(Bayer),  Michigan  Amber,  and  Michigan  Wonder  No.  211  occurred 


Experime:nts  in  Field  Plot  Technic 


33 


in  the  order  named  in  four  distributed  sections  of  the  field.  The  aver- 
age yields  of  these  varieties  in  the  four  series,  in  bushels  per  acre,  for 
border  rows  and  for  interior  rows,  are  shown  below,  together  with 
the  average  dates  of  heading,  dates  of  maturity,  and  heights,  also  de- 
termined for  the  four  series. 


23.  Fultz  (Bayer) 

39.  Michigan  Amber 

55.  Michigan  Wonder 
No.   211 

Row 

1 

Row 
2.3,4 

Row 

5 

Row 
1 

Row 
2,3,4 

Row 

5 

Row 

1 

Row 
2,3,4 

Row 

5 

Average 
yields 

10.8 
bu. 

12.2 
bu. 

13.1 
bu. 

13.3 
bu. 

14.9 
bu. 

14.5 
bu. 

19.8 
bu. 

18.1 
bu. 

19.4 
bu. 

Average 
-late  of 
heading 

21* 

21* 

19* 

Average 
date  of 
maturity 

47* 

48* 

47* 

Average 
height 

43  in. 

42  in. 

43  in. 

*   Dates  of  heading  and  maturity   are   the   numbers   of  days   after  April   30.     Thus    1    is 
May  1,  32  is  June  1,   47  is  June  16,  etc. 


Now  dividing  the  yields  in  border  rows  by  the  yields  of  the  same 
varieties  in  interior  rows,  we  obtain  the  relative  border  yields,  which 
are  substituted  in  the  table  below  for  the  border  yields  in  bushels. 
To  determine  the  degree  of  competition  between  the  varieties  Fultz  and 
Michigan  Amber  we  divide  the  larger  relative  border  yield  (107)  by  the 
smaller  (89)  and  subtract  100,  giving  20  per  cent.  Since  in  this  case  the 
relative  border  yield  of  the  variety  on  the  left  is  higher,  the  difference  is 
given  a  minus  sign.  Similarly  a  value  of  +12  per  cent  is  obtained  for 
the  competition  between  Michigan  Amber  and  Michigan  Wonder  No. 
211.  These  figures  mean  that  the  relative  border  yield  of  Fultz  ex- 
ceeded that  of  Michigan  Amber  by  20  per  cent  in  their  competing 
border  rows,  while  that  of  Michigan  Wonder  exceeded  that  of  Michi- 
gan Amber  by  12  per  cent. 

The  relative  yields  of  these  varieties  are  obtained  similarly, — 
in  the  first  case  by  dividing  14.9  by  12.2  (+22%)  and  in  the  second 
case  by  dividing  18.1  by  14.9  (+21%).  Both  values  are  positive  be- 
cause in  each  case  the  yield  of  the  variety  on  the  left  is  higher  than 
that  of  the  variety  on  the  right.  The  difference  in  dates  of  heading, 
maturity,  and  height  are  obtained  simply  by  subtraction,  being  positive 
when  the  value  of  the  variety  on  the  right  is  greater  and  negative  when 


34 


Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 


the  value  of  the  variety  on  the  left  is  greater.    The  figures  ready  for 
correlation  study  will  then  appear  as  follows : 


Row 
1 

23.  Fultz 
(Bayer) 

Row       Row 
2,  3,  4          5 

Compe- 
tition 
data 

39.  Michigan 
Amber 
Row         Row     Row 
1         2.  3, 4       5 

Compe- 
tition 
data 

55. Michigan  Wonder 

No.  211 

Row     Row         Row 

1         2,3,4        5 

Average 
yield 

89 

12.2 

107 

-20% 
+22% 

89 

14.9 

97 

+  12% 
+21% 

109 

18.1 

.0. 

Average 
date  ot 
heading 

21 

0 

21 

-2 

19 

Average 
date  of 
maturity 

47 

+  1 

48 

0 

47 

Average 
height 

43 

-1 

42 

+  1 

43 

The  columns  headed  "competition  data"  show  the  relation  of  the 
effect  of  competition  to  the  yield,  earliness,  and  height  of  the  competing 
varieties.  For  example,  Michigan  Amber  was  at  a  disadvantage  of  20 
per  cent  in  competition  with  Fultz,  though  it  was  22  per  cent  superior 
in  yield  when  protected  from  competition.  It  headed  the  same  day, 
matured  one  day  later,  and  was  one  inch  shorter.  After  correspond- 
ing data  had  been  prepared  for  all  the  96  varieties  in  this  test,  correla- 
tion tables  with  the  coefficient  of  competition  as  subject  and  relative 
yield,  date  of  heading,  date  of  maturity,  and  height  as  relative  were 
constructed.  Correlations  were  determined  similarly  in  the  other  tests. 
One  of  these  correlation  tables  is  shown  in  figure  6.    In  general,  merely 


1 

1 

o 

00 

1 

1 

o 

1 

I 

S 

o 

o 

g 

B 

B 

B 

B 

B 

B 

o 

B 

B 

B 

B 

B 

1 
1 

1 

I 

5 
1 

1 

o 

o 

o 

o 

g 

g 

—40  to   —60 

1 

1 

—20   to   —40 

2 

1 

1 

2 

4 

2 

2 

14 

0   to    —20 

1 

1 

7 

10 

5 

2 

26 

0  to       20 

1 

2 

6 

10 

8 

3 

5 

35 

20   to       40 

2 

3 

4 

11 

2 

1 

1 

24 

40   to       60 

1 

1 

3 

5 

60   to       80 

1 

1 

1 

3 

Total 

2 

1 

3 

5 

20 

26 

21 

16 

8 

5 

1 

112 

FiGURB   6.— -CORREI^ATION    BETWEEN    COEFFICIENT   OF    COMPETITION   AND    RELA- 
TIVE Yield,  in  Wheat  Variety  Test  1920. 

r=     +.582  ±     .043. 


Experime:nts  in  Fie:i.d  Plot  Technic  35 

the  coefficient  of  correlation  and  its  probable  error  are  given,  for  lack 
of  space. 

In  the  barley  variety  test,  1919,  the  effect  of  competition  was  quite 
marked.  The  average  yield  of  border  rows  differed  from  the  average 
yield  of  interior  rows  by  11.13  per  cent,  and  the  mean  coefficient  of 
competition  was  21.30  per  cent.  Attempts  were  made  to  correlate 
competition  with  relative  date  of  heading,  date  of  maturity,  grain-straw 
ratio,  and  yield.  The  correlation  coefficients  determined  are  shown 
in  Table  10,  together  with  the  mean  differences  between  competing 

Table  10. — Correlation  oe  Competition  With  Various  Characteristics  in 
Barley  Varety  Test  1919. 


Character 

Mean  difference  be- 

Coefficient of  correlation 

tween  competing 

with  competition 

varieties 

Date  of  heading 

4.0  days 

—.153  ±.120 

Date  of  maturity 

2.6  days 

—.063  ±.123 

Grain-straw  ratio 

38.0% 

-1-.072  ±.122 

Yield 

52.3% 

4- .442  ±.099 

varieties  in  the  characters  whose  relation  to  competition  was  studied. 
Although  none  of  these  correlations  is  statistically  significant,  in 
the  strictest  sense,  it  is  noticeable  that  the  correlation  between  compe- 
tition and  yield  is  much  greater  than  any  of  the  others,  and  is  equal 
to  about  four  and  one-half  times  its  probable  error.  There  was  ap- 
parently some  tendency  for  the  better  yielding  varieties  to  profit  by 
competition  with  the  poorer  yielders.  On  account  of  the  relatively 
small  number  of  cases  involved  in  this  and  the  other  1919  tests,  the 
probable  errors  are  high,  and  a  fairly  high  coefficient  of  correlation 

Table  11. — Correlation  of  Competition  With  Various  Characteristics  in 
Oats  Variety  Test  1919. 


Character 

Mean  difference  be- 

Coefficient of  correlation 

tween  competing 

with  competition 

varieties 

Date  of   maturity 

3.56  days 

—.456  ±.103 

Grain-straw  ratio 

50.2% 

—.091  ±.129 

Yield 

53.5% 

-f.314  ±.117 

may  consequently  fail  to  attain  statistical  significance.  Such  a  co- 
efficient, while  not  establishing  the  correlation,  by  no  means  indicates 
that  the  correlation  does  not  exist. 


36  Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 

The  oats  variety  test  of  1919  also  showed  distinctly  the  effects 
of  competition.  The  border  rows  in  this  test  differed  in  yield  from 
the  interior  rows  by  12.78  per  cent,  on  the  average,  and  the  mean 
coefficient  of  competition  was  27.67  per  cent.  Correlations  were  de- 
termined for  competition  and  relative  yield,  date  of  maturity,  and 
grain-straw  ratio.  Unfortunately  the  dates  of  heading  are  not  avail- 
able for  all  varieties  in  this  test.  The  correlation  coefficients  are  shown 
in  Table  11. 

Again  no  correlations  of  statistical  significance  are  found,  but 
the  relation  of  yield  and  earliness  of  maturity  to  competing  strength 
is  at  least  suggestive.  There  was  a  tendency  for  early  and  high-yielding 
varieties  to  profit  by  competition  at  the  expense  of  later  and  lower -yield- 
ing varieties,  but  the  number  of  varieties  was  too  small  to  permit  the 
drawing  of  positive  conclusions. 

The  oats  strains  grown  on  the  same  field  showed  much  less  strik- 
ingly the  effects  of  competition.  The  mean  difference  in  yield  be- 
tween border  rows  and  interior  rows  in  these  15  strains  was  only  6.50 
per  cent  and  the  mean  coefficient  of  competition  only  13.11  per  cent. 
This  is  undoubtedly  accounted  for  by  the  fact  that  the  differences  be- 
tween competing  strains  were  so  much  less  than  in  the  oats  variety 
test.  When  the  three  strains  taxonomically  unlike  Red  Rustproof  are 
eliminated,  leaving  12  strains  of  the  same  variety,  the  average  devia- 
tion of  border  yields  from  interior  yields  is  reduced  to  4.69  per  cent 
and  the  average  coefficient  of  competition  to  8.69  per  cent.  It  is  note- 
worthy that  the  competition  between  these  strains  of  the  same  va- 
riety is  decidedly  less  than  that  between  different  varieties.     No  sig- 


TaBLE    12. — CORREI^ATION    OF    COMPETITION    WiTH    VARIOUS    CHARACTERISTICS    IN 

Oats  Strain  Test  I9ii9. 

Character  Mean  difference  be-        Coefficient  of  correlation 

tween  competing  with  competition 

strains 


Date  of  heading 

2.67  days 

—.376  ±.136 

Date  of  maturity 

1.56  days 

—  .244  ±.149 

Grain-straw  ratio 

14.2% 

-{-.012  ±.159 

Yield 

17.1% 

-J-.316  ±.143 

nificant  correlation  was  found  between  these  minor  effects  of  compe- 
tition (for  the  15  strains)  and  the  relative  time  of  heading,  time  of 
maturity,  grain-straw  ratio  or  yield,  as  is  shown  in  Table  12,  though 
in  this  case  again  the  early  strains  and  the  high-yielding  strains  showed 
some  tendency  to  profit  by  competition. 


Expe:rime:nts  in  Field  Plot  Technic  37 

In  the  wheat  variety  test  of  1920  the  average  yield  of  border  rows 
differed  from  the  average  yield  of  interior  rows  by  12.30  per  cent  and 
the  mean  coefificient  of  competition  was  19.79  per  cent.  These  figures 
represent  the  average  determinations  when  the  two  varieties  of  rye 
and  the  border  yields  of  the  varieties  of  wheat  adjoining  them  were 
eliminated.  The  correlation  between  competition  and  relative  yield, 
date  of  heading,  and  date  of  maturity  were  determined  for  this  test 
and  the  coefficients  of  correlation  are  shown  in  Table  13. 

Tabi,e  13. — Correlation  of  Competition  With  Various  Characteristics  in 
Wheat  Variety  Test  1920. 

Character  Mean  difference  be-        Coefficient  of  correlation 

tween  competing  with  competition 

varieties 

Date  of  heading  2.3  days  — .515  ±.048 

Date  of  maturity  2.7  days  — .552  ±.045 

Yield  28.9%  +.582  ±.043 

Competition  in  this  test  was  negatively  correlated  with  earliness  of 
heading  and  maturity  and  positively  with  yield.  All  of  the  correla- 
tion coefficients  are  clearly  significant.  In  other  words,  there  was  a 
rather  pronounced  tendency  for  the  early  and  high-yielding  varieties 
to  profit  in  competition.  To  a  considerable  extent  the  early  varieties 
were  the  high  yielding  varieties  in  this  test,  as  indicated  by  the  fact 
that  the  correlation  coefficient  for  date  of  heading  and  yield  was  —.511 
±.051,  and  that  for  date  of  maturity  and  yield  was  —.642  ±.041.  Al- 
though it  is  clear  from  these  results  that  early,  high-yielding  varieties 
excelled  in  competition,  it  is  not  clear  whether  they  did  so  chiefly  as  a 
result  of  their  earliness  or  chiefly  as  a  result  of  their  yield. 

Table  14.— CorreivATion  oe  Competition  With  Various  Characteristics  in 
Wheat  Variety  Test  1921. 

Character  Mean  difference  be-        Coefficient  of  correlation 

tween  competing  with  competition 

varieties 


Date  of  heading 

2.1  days 

—.271  ±.060 

Date  of  maturity 

1.6  days 

—.222  ±.062 

Height 

3.3  inches 

-I-.347  ±.057 

Yield 

19.5% 

+.294  ±.059 

k 


Similar  results  were  obtained  in  the  wheat  variety  test  of  1921 
in  which  the  difference  between  the  average  yield  of  border  and  in- 
terior rows  was  12.89  per  cent  and  the  mean  coefficient  of  competition 


38  Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 

was  18.85  per  cent.  Correlations  were  determined  for  competition  and 
relative  yield,  date  of  maturity,  date  of  heading,  and  height  in  this 
test.  The  coefficients  of  correlation  thus  determined  are  shown  in 
Table  14. 

In  this  case,  as  in  the  wheat  variety  test  of  the  preceding  season, 
dates  of  heading  and  maturity  were  correlated  negatively  and  yield 
was  correlated  positively  with  competition.  The  coefficients  of  correla- 
tion were  materially  lower,  and  in  fact  are  hardly  significant.  It  is  in- 
teresting that  in  this  case  height  was  correlated  more  closely  with 
competition  than  were  either  earliness  or  yield.  In  this  season  again 
earliness  was  correlated  to  some  extent  with  yield,  the  coefficients  of 
correlation,  for  date  of  heading  and  yield  being  — .331  ±.062  and  for 
date  of  maturity  and  yield  —.419  —.057. 

In  the  wheat  mixture  test  of  1921  the  varieties  were  grouped 
roughly  in  respect  to  earliness,  and  in  only  three  cases  was  there  a 
greater  difference  than  two  days  in  heading  or  maturity  between  ad- 
jacent varieties.  The  rows  in  this  test  ran  north  and  south.  The 
conditions  may  be  considered  favorable  in  this  test  for  the  reduction 
of  competition.  Nevertheless  the  average  yield  of  border  rows  dif- 
fered from  that  of  interior  rows  by  10.07  per  cent  and  the  mean  co- 
efficient of  competition  was  14.28  per  cent.  The  coefficients  of  correla- 
tion determined  for  competition  and  date  of  heading,  date  of  maturity, 
and  yield,  are  shown  in  Table  15. 

TaBI,E    15. — CORREI/ATION    OF    COMPETITION    WiTH    VARIOUS    CHARACTERISTICS    IN 

Wheat  Mixture  Test  1921. 

Character  Mean  difference  be-        Coefficient  of  correlation 

tween  competing  with  competition 

varieties 


Date  of  heading  1.2  days  —.514  ±.083 

Date  of  maturity  0.8  days  —.613  ±.070 

Yield  19.2%  -h  .554  ±.078 

In  this  test  significant  negative  correlations  between  competition 
and  dates  of  heading  and  maturity  and  a  significant  positive  correla- 
tion between  competition  and  yield  are  shown.  The  tendency  for 
early,  high-yielding  varieties  to  profit  by  competition  was  about  as 
strong  as  in  the  wheat  variety  test  of  the  preceding  season,  though  the 
extent  of  competitive  effect  was  considerably  reduced. 

The  effects  of  competition  in  the  oats  variety  test  in  1921  were 
extreme.  The  yields  of  border  rows  differed  by  16.74  per  cent,  on 
the  average,  from  the  yields  of  interior  rows,  and  the  mean  coefficient 
of  competition  was  39.15  per  cent.     The  extreme  effects  of  compe- 


Experiments  in  Fiei.d  Plot  Technic  39 

tition  in  this  test  are  probably  accounted  for  by  the  fact  that  the  va- 
rieties differed  very  widely  in  varietal  type  and  in  yield.  Differences 
of  as  much  as  17  days  in  date  of  heading,  13  days  in  date  of  maturity, 
and  almost  200  per  cent  in  yield,  were  involved.  The  correlations  de- 
termined between  competition  and  relative  date  of  heading,  date  of 
maturity  and  yield,  are  shown  in  Table  16. 

Table  16.— Correi^ation  of  Competition  With  Various  Characteristics  in 

Oats  Variety  Test  1921. 

Character  Mean   difference   be-        Coefficient   of   correlation 

tween   competing  with   competition 

varieties 


Date   of   heading 

4.8  days 

—.648  ±.060 

Date  of  maturity- 

4.1  days 

—.860  ±.028 

Yield 

51.1% 

4- .484  ±.082 

A  remarkably  high  negative  correlation  between  date  of  maturity 
and  competition  is  shown.  The  negative  correlation  between  date  of 
heading  and  yield  is  also  quite  high,  while  the  positive  correlation  be- 
tween yield  and  competition  is  barely  significant.  In  this  test,  in  which 
extreme  differences  in  time  of  maturity  occurred,  the  early-maturing 
varieties  had  a  very  distinct  advantage  in  competition  with  the  later 
varieties.  Earliness  was  very  closely  correlated  with  yield  in  the  oats 
variety  test  of  this  season,  the  coefficient  of  correlation  for  date  of 
heading  and  yield  being  —.750  =^.052  and  that  for  date  of  maturity  and 
yield  being  —.894  ±.024.  Considering  the  close  correlation  of  earliness 
and  yield,  and  the  relatively  low  correlation  of  yield  and  competition, 
it  would  seem  that  the  latter  may  be  merely  a  by-product  of  the  rela- 
tion of  earliness  to  competition.  Since  the  early  varieties  were  the 
leaders  both  in  competition  and  in  yield,  some  correlation  of  yield  and 
competition  is  inevitable. 

In  the  oats  strains  test  of  1921  Kherson  and  Red  Rustproof  strains 
were  alternated  and  both  a  Kherson  and  a  Red  Rustproof  check  were 
grown.  In  most  cases  therefore  the  competing  border  rows  repre- 
sented these  two  varieties,  though  in  some  cases  two  Red  Rustproof 
or  two  Kherson  plots  occurred  together,  as  is  shown  in  the  planting 
plan  in  figure  5.  The  effects  of  competition  in  this  plot  were  quite 
distinct,  as  is  to  be  expected,  though  they  were  not  so  extreme  as  in 
the  oats  variety  test  discussed  above,  which  was  located  on  the  same 
field.  The  average  yield  of  border  rows  differed  from  the  average  yield 
of  interior  rows  by  11.76  per  cent.  The  mean  coefficient  of  compe- 
tition was  23.85  per  cent. 

When  we  exclude  the  competition  between  the  three  strains  not 
true  to  name  and  the  strains  adjacent  to  each,  that  between  the  Kher- 


40 


Missouri  Agr.  Exp.  Sta.  Re:search  Bui^letin  49 


son  and  Red  Rustproof  check  plots,  and  that  between  adjacent  strains 
of  the  same  variety,  58  cases  of  competition  between  different  strains 
of  Kherson  and  Red  Rustproof  remain.  In  these  the  mean  yield  of 
border  rows  differed  from  that  of  interior  rows  by  14.06  per  cent  and 
the  mean  coefficient  of  competition  was  30.86  per  cent.  In  every  case 
the  Kherson  strain  outyielded  the  adjacent  Red  Rustproof  strain, 
though  the  advantage  in  yield  varied  from  27  per  cent  to  165  per  cent. 
Similarly,  the  Kherson  strains  were  earlier  in  maturity  and  heading, 
and  taller,  in  each  case,  but  with  a  rather  wide  variation  in  the  extent 
of  their  advantage.  In  all  but  three  of  the  58  cases  the  Kherson  strains 
showed  a  greater  advantage  in  yield  over  the  adjacent  Red  Rustproof 
strains  in  their  competing  border  rows  than  in  their  interior  rows. 
The  average  yields  of  the  30  Red  Rustproof  strains  and  29  Kherson 
strains,  in  interior  rows  and  competing  border  rows,  were  as  follows : 


Average  yield  in 
interior  rows 

Average  yield  in 
competing  border 
rows 

Bushels 

Relative 

Bushels 

Relative 

Red  Rustproof  strains 
Kherson  strains 

21.00 
35.79 

100 
170 

18.59 
41.00 

100 
222 

The  Kherson  strains  outyielded  the  Red  Rustproof  strains  by  70 
per  cent  in  their  interior  rows  and  by  122  per  cent  in  their  competing 
border  rows.  The  coefficients  of  competition,  like  the  relative  yield, 
earliness,  and  height,  varied  rather  widely.  Correlations  were  there- 
fore measured  for  the  advantage  of  the  Kherson  strain  of  each  adjacent 
pair  in  competition  and  its  advantages  in  yield,  date  of  heading,  date 
of  maturity,  and  height.  The  coefficient  of  correlation  in  each  case 
was  insignificant. 


Discussion. — In  each  of  these  tests,  with  the  exception  of  the 
oats  strain  test  of  1919,  in  which  most  of  the  strains  compared  be- 
longed to  the  same  variety,  border  rows  differed  from  interior  rows  in 
yield  by  more  than  10  per  cent.  Differences  as  great  as  this  will  change 
materially  the  relative  standing  of  varieties.  In  single-row  tests  the 
effects  of  competition  would  be  considerably  greater  than  in  these 
border  rows,  affected  by  competition  on  only  one  side.  Furthermore, 
in  each  test,  of  course,  there  were  many  cases  in  which  competition 
caused  much  larger  differences  in  yield  than  are  shown  by  average 
figures. 


Experiments  in  Field  Plot  Technic 


41 


The  relation  of  the  direction  of  rows  to  the  effects  of  varietal  com- 
petition is  not  clearly  shown  by  these  experiments.  The  tests  which 
showed  least  the  effect  of  competition,  the  oats  strain  test  of  1919 
and  the  wheat  mixture  test  of  1921,  were  in  rows  running  north  and 
south.  But  relatively  little  effect  from  competition  is  to  be  expected 
in  these  tests,  regardless  of  the  direction  of  the  rows,  because  of  the 
similarity  of  adjacent  strains.  In  the  oats  strain  test  12  of  the  15 
strains  were  taxonomically  identical,  and  it  has  been  shown  that  the 
effects  of  competition  among  these  was  much  less  than  among  the 
strains  of  different  varieties.  In  the  wheat  mixture  test  the  varieties 
making  up  each  mixture,  which  were  grown  side  by  side  in  the  test, 
were  chosen  partly  for  their  similarity  in  time  of  maturity,  and  the 
differences  between  adjacent  varieties  were  therefore  considerably 
less  than  in  the  wheat  variety  test  of  the  same  season.  It  cannot  be 
stated  definitely,  therefore,  from  the  results  of  these  tests,  that  tests 
in  rows  running  north  and  south  are  either  more  or  less  subject  to  error 
from  competition  than  tests  in  rows  running  east  and  west.  It  is 
clear,  however,  that  a  considerable  error  from  varietal  competition 
may  occur  in  tests  in  which  the  rows  run  north  and  south,  as  is  evi- 
denced particularly  by  the  barley  and  oats  variety  tests  of  1919. 

The  relation  of  competition  to  relative  date  of  heading,  date  of 
maturity,  grain-straw  ratio,  height,  and  yield,  insofar  as  it  was  in- 
vestigated in  these  experiments,  is  shown  in  summary  form  in  Table 
17.     Although  none  of  these  characteristics  shows  a  significant  rela- 


TabIvE  17. — Summary  of  Effects  of  Competition  in  Ali,  Tests. 


Test 


u   • 

. 

o  . 

^ 

^si 

iB     o 

CO 

55 

1=8 

1919 

27 

21.30 

1919 

24 

27.67 

1919 

15 

13.11 

1920 

94 

19.79 

1921 

94 

18.85 

1921 

30 

14.28 

1921 

32 

39.15 

Date    of 
Heading . 


Coefficient   of    Correlation    between    Competition   and- 


Date  of 
Maturity. 


Grain- Straw 
Ratio. 


Height. 


Yield. 


Barley   variety 
Oats   variety 
Oats    strain 
Wheat    variety 
Wheat   variety 
Wheat    mixtiire 
Oats    variety 


— .153±.120 

-.376±.136 
— .5l5±.048 
-.271±.060 
—  .514+.083 
— .648+.060 


.063±.123 
.456±.103 
.244±.157 
.552±.045 
.222±.062 
.613±.07O 
.860±.028 


+  .072±.122 
— .091±.129 
+.012±.159 


+.347±.057 


+  .442±.099 
4-.314±.117 
+  .316±.143 
+  .582±.043 
+  .294±.059 
+  .554±.078 
+.484±.082 


tion  to  competition  in  every  case,  the  results  of  the  tests  are  fairly 
consistent.  The  correlation  of  competition  with  yield  is  always  posi- 
tive, and  is  fairly  high  in  every  case,  the  lowest  coefficient  being  +.294 
—.059.  From  these  results  there  can  be  no  doubt  that  the  higher  yield- 
ing varieties  are  those  which  in  general  have  profited  by  competition. 
The  date  of  heading  and  the  date  of  maturity  show  a  negative  correla- 


42  Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 

tion  with  competition  in  each  case,  though  some  of  the  coefficients 
are  insignificant.  It  is  clear  therefore  that  early  varieties  are,  in  gen- 
eral, able  to  compete  more  strongly,  but  the  extent  of  this  relation  is 
quite  variable.  The  grain-straw  ratio  showed  no  significant  relation 
to  competition  in  any  of  the  experiments  of  1919,  and  was  not  deter- 
mined for  the  succeeding  tests.  Height  was  correlated  positively  with 
competition  in  the  one  test  in  which  height  was  determined,  the  wheat 
variety  test  of  1921.  In  this  test  height  was  more  closely  related  to 
competition  than  were  date  of  heading,  date  of  maturity,  or  yield. 

In  the  oats  variety  tests,  the  relation  of  early  maturity  to  compe- 
tion  is  particularly  marked,  the  coefficients  of  correlation  in  both  oats 
variety  tests  being  distinctly  greater  for  date  of  maturity  and  compe- 
tition than  for  yield  and  competition.  In  the  wheat  tests  there  was 
little  difference  in  the  degree  of  relation  to  competition  between  earli- 
ness  and  yield.  In  the  one  test  of  barley  varieties  conducted,  yield 
was  more  closely  correlated  with  competition  than  was  either  the 
date  of  heading  or  date  of  maturity,  but  none  of  the  three  showed  a 
clearly  significant  correlation. 

It  is  clear  that  in  these  trials  the  early,  high-yielding  varieties 
profited  by  competition.  To  a  considerable  extent  these  may  be  the 
same  varieties,  for  the  correlation  of  earliness  and  yield  was  high  in 
most  of  the  tests  conducted.  The  relation  of  earliness  and  other 
characters  to  yield  under  Missouri  conditions  will  be  considered  more 
fully  in  another  paper,  but  data  of  interest  in  this  connection  are  ap- 
propriate here.  The  coefficients  of  correlation  of  yield  with  date  of 
heading  and  date  of  maturity  in  the  variety  tests  discussed  in  this 
paper  are  shown  in  Table  18. 

TaBI,E  18. — CoRREIvATION  OF  YiELD  WiTH   DaTES  OF  HEADING  AND   MATURITY  IN 

Variety  Tests  oe  Bari,ey,  Oats,  and  Wheat 

Coefficient  of  correlation  of 
Number  of  yield  with — 

Crop  Season    varieties  Date  of  heading  Date  of  maturity 


Barley 

1919 

27 

—.281  ±.120 

—  .271  ±.120 

Oats 

1919 
1921 

40 
32 

—.627  -4- .065 

Oats 

—.750  ±.052 

—  .894  ±.024 

Wheat 

1920 

94 

—.511  ±.051 

—.642  ±.041 

Wheat 

1921 

94 

—.331  ±.062 

—.419  ±.057 

When  a  very  high  correlation  exists  between  earliness  and  yield 
it  is  likely  that  a  character  closely  correlated  with  one  may  show  a 
high  degree  of  correlation  with  the  other,  which  might  not  be  shown 
were  it  not  for  the  first  correlation.     For  example,  suppose  earliness 


Experime:nts  in  Field  Plot  Technic  43 

of  maturity  is  largely  responsible  for  strong  competitive  value.  Then 
in  a  season  when  earliness  is  closely  correlated  with  yield  a  close  cor- 
relation of  competition  and  yield  is  likely  to  be  found,  not  because  high 
yield  makes  for  strong  competition  but  because  the  high-yielding  va- 
rieties are  early.  Conversely,  the  competing  value  may  be  dependent 
on  the  yield  and  the  correlation  with  earliness  may  be  incidental,  under 
the  same  conditions.  If  the  relation  of  earliness  and  yield  were  con- 
stant, such  a  question  would  have  little  practical  importance,  but  when 
the  relation  is  reversed,  as  it  may  be  in  different  localities  and  even  in 
different  seasons  in  the  same  locality,  the  relation  of  competition  to 
the  two  characteristics  may  be  very  different.  The  relation  of  compe- 
tition to  earliness  and  yield  in  these  tests,  therefore,  may  be  due  pri- 
marily to  the  predominating  influence  of  either  of  these  two  charac- 
teristics, or  to  the  influence  of  both. 

General  conclusions  regarding  competition  should  not  be  drawn 
from  these  tests.  The  problem  of  competition  is  complicated  by  many 
factors,  and  will  require  numerous  and  extensive  investigations  for 
its  solution.  These  results,  however,  indicate  that  gross  errors  from 
this  source  are  commonly  involved  in  variety  tests,  that  such  errors 
occur  both  in  rows  running  east  and  west  and  in  rows  running  north 
and  south,  that  the  error  is  less  when  the  varieties  and  strains  com- 
pared are  structurally  similar  than  when  they  are  widely  different,  and 
that  the  error  may  be  reducible  to  some  extent  by  the  grouping  of  va- 
rieties according  to  the  time  of  maturity  and  possibly  other  characters, 
when  the  relation  of  such  characters  to  competition  is  more  fully 
studied.  In  the  present  state  of  knowledge  regarding  the  relation  of 
competition  to  the  characteristics  of  the  varieties  compared,  the  use 
of  border  rows  is  highly  desirable,  since  by  their  use  the  error  from 
competition  can  be  practically  eliminated. 

SIZE  AND  REPLICATION  OF  PLOTS. 

Previous  Investigation. — Most  of  the  direct  evidence  reported 
on  replication  and  size  of  plots  has  been  obtained  in  experiments  in 
which  a  field  of  a  uniformly  handled  crop  is  harvested  in  a  large  num- 
ber of  small  sections.  These  sections  are  grouped  to  form  plots  of 
different  shapes  and  sizes,  and  systematically  distributed  sections  are 
averaged  to  represent  replicate  plots.  The  relative  variability  of  the 
yields  determined  by  each  plot  arrangement  is  the  criterion  of  expe- 
rimental accuracy.  Such  experiments  have  been  reported  by  Morgan" 
with  wheat  and  fodder  corn.  Wood  and  Stratton"  with  mangels,  Mer- 
cer and  Hall  "  with  wheat  and  mangels,  Hall  and  Russell'  with  wheat, 


44  Missouri  Agr.  Exp.  Sta.  Re:search  Bulletin  49 

Montgomery"'"  with  wheat,  Kiesselbach"  with  oats,  and  Day*  with 
wheat. 

The  general  conclusions  drawn  from  these  experiments  are  in 
harmony,  though  the  specific  size  and  shape  of  plot  and  number  of 
replications  found  most  desirable  vary  rather  widely.  In  general,  plot 
variability  was  reduced  by  increasing  the  size  of  the  individual  plot, 
up  to  a  certain  limit,  but  it  was  reduced  much  more  eflf,ectively  by  rep- 
lication of  plots.  For  a  given  area  a  large  number  of  small  plots  was 
always  found  more  accurate  than  a  small  number  of  large  plots. 

But  the  size  of  the  plot  cannot  be  reduced  indefinitely  for  several 
reasons.  As  the  plot  becomes  smaller  the  proportion  subject  to  "bor- 
der effect"  rapidly  becomes  greater.  This  border  effect  may  be  due 
to  the  modified  growth  of  plants  adjoining  an  alley  or  to  the  in- 
fluence of  the  competition  of  different  varieties  in  adjacent  rows.  If 
the  borders  are  not  discarded  an  important  systematic  error  is  involved ; 
if  they  are  discarded  a  considerable  portion  of  the  land  and  labor  is 
lost.  In  either  case  the  disadvantage  is  increased  as  the  size  of  the 
plot  is  decreased.  When  single  rod-row  plots  ar.e  used  the  whole 
plot  is  subject  to  border  effect.  ,The  importance  of  this  error  has 
already  been  discussed.  Another  disadvantage  of  the  extremely 
small  plot  is  that  slight  differences  in  stand  and  small  mechanical  er- 
rors have  a  marked  effect  on  the  yields.  The  increased  labor  involved 
in  handling  a  large  number  of  small  plots  rather  than  a  small  number 
of  large  plots  is  also  an  important  disadvantage. 

The  length  of  the  so-called  rod-row  has  usually  been  determined 
by  convenience.  Commonly  used  lengths  when  the  rows  are  a  foot 
apart  are  16  feet  for  wheat,  20  feet  for  barley,  and  15  feet  for  oats, 
since  with  these  lengths  yields  in  grams  per  row  may  easily  be  con- 
verted to  bushels  per  acre.  In  other  cases  the  most  convenient  length 
is  determined  by  the  dimensions  of  experiment  fields.  Although  in- 
creasing the  length  of  the  row  would  doubtless  reduce  variability,  a 
greater  gain  could  be  made  on  the  same  area  by  further  replication. 
Ordinarily  it  is  preferable,  therefore,  to  retain  the  most  convenient 
length  and  to  make  any  desired  increase  in  size  of  plot  in  the  width, 
for  widening  the  plots  will  rapidly  reduce  the  proportion  subject  to 
border  effect. 

Experimental  Residts.  —Size  of  Plots. — By  comparing  the  stand- 
ard deviations  of  single  rows  and  blocks  consisting  of  three  and  five 
rows  each,  in  the  check  plots,  it  is  possible  to  determine  the  relative 
value  of  plots  of  the  three  sizes  in  counteracting  plot  variability.  In 
this  comparison  the  single-row  and  three-row  plots  correspond  respec- 
tively to  3-row  and  5-row  plots  in  which  the  border  rows  are  dis- 


Experiments  in  FieivD  Plot  Technic 


45 


carded,  since  they  are  made  up  of  rows  protected  from  varietal  compe- 
tition by  border  rows.  In  each  of  the  computations  summarized  be- 
low each  check  plot  is  represented  by  only  one  yield.  For  example,  in 
determining  the  yield  and  standard  deviation  of  single  rows  in  the  20 
check  plots  of  the  oats  variety  test  of  1919,  the  constants  for  single 
rows  are  the  average  of  determinations  made  independently  for  Row 
2  of  each  of  the  20  plots,  for  Row  3,  and  for  Row  4.  The  determina- 
tions for  3-row  plots  are  similarly  made  from  the  computed  yields  of 
the  three  interior  rows  of  each  check  plot,  and  those  for  5-row  plots 
from  the  computed  yields  of  the  entire  plots.  Thus  each  determination 
represents  the  same  number  of  plots  and  the  same  area,  the  only  dif- 
ference being  in  the  size  of  the  individual  plot.  It  would  be  possible, 
of  course,  to  test  40  per  cent  more  varieties  with  the  same  number  of 
replications  or  to  increase  the  number  of  replications  by  40  per  cent 
for  the  same  number  of  varieties  on  the  same  area,  if  3-row  blocks 
were  used  rather  than  5-row  blocks. 

The  yield  and  variability  of  check  plots  of  different  sizes  in  the 
barley  variety  test  of  1919  are  shown  in  Table  19.  The  variety  grown 
in  these  check  plots  was  Oderbrucker,  seeded  at  the  rate  of  8  pecks 
per  acre.    The  check  variety  was  grown  in  every  sixth  plot. 


Table  19. — Yield  and  Variability  of  Check  Plots. 
Single-row,   Three-row,   and  Five-row — Barley  Variety  Test  1919. 


Number 

Yield 

Size  of  plot 

of  plots 

per  acre 

Standard  deviation 

bu. 

bu. 

% 

Single-row 

Row  1 

21 

41.26 

7.95 

19.26 

Row  2 

21 

36.71 

8.30 

22.61 

Row  3 

21 

37.15 

8.48 

22.84 

Row  4 

21 

35.82 

10.37 

28.96 

Row  5 

21 

42.12 

11.86 

28.16 

Mean  of  three 

interior  rows 

21 

36.56 

9.05 

24.80 

Mean  of 

five  rows 

21 

38.61 

9.39 

24.37 

Three-row  Plot 

(Interior  rows) 

21 

36.56 

8.11 

22.18 

Five-row  Plot 

21 

38.61 

8.29 

21.47 

The  variability  of  the  single-row  plots  is  12  per  cent  higher  on 
the  average  than  that  of  the  3-row  plots.     That  is,  3-row  plots  with 


46 


Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 


borders  discarded  would  have  given  in  this  case  somewhat  more  va- 
riable results  than  5-row  blocks  with  borders  discarded.  The  same  5- 
row  blocks  harvested  entire  (with  borders  retained)  gave  slightly  less 
variable  yields  than  when  the  borders  were  discarded. 

The  same  comparison  may  be  made  in  the  check  plots  of  the 
oats  variety  test  of  1919.  The  check  variety  was  Red  Rustproof, 
drilled  at  the  rate  of  10  pecks  per  acre  in  every  ninth  plot.  The  re- 
sults are  shown  in  Table  20. 

TABr,E  20. — Yield  and  Variabiuty  of  Check  Plots. 
Single-row,  Three-row,  and  Five-row — Oats  Variety  Test  1919. 


Number 

Yield 

Size  of  plot 

of  plots 

per  acre 

Standard  deviation 

Single-row 
Row  1 

20 

bu. 
44.64 

bu. 
10.37 

% 
23.23 

Row  2 

20 

47.97 

9.81 

20.45 

Row  3 

20 

46.56 

11.42 

24.53 

Row  4 

20 

46.95 

13.81 

29.41 

Row  5 
Mean  of  three 

20 

42.09 

11.58 

27.51 

interior  rows 
Mean  of 

20 

47.16 

11.68 

24.80 

five  rows 
Three-row  Plot 

(Interior  rows) 
Five-row  Plot 

20 
20 
20 

45.64 
47.16 
45.64 

11.40 

10.62 

9.72 

25.03 
22.59 
21.30 

The  results  in  this  case  are  practically  identical  with  those  of  the 
barley  variety  test.  Protected  single  rows  were  10  per  cent  more  va- 
riable than  protected  3-row  blocks,  while  the  latter  were  only  6  per 
cent  more  variable  than  unprotected  5-row  blocks. 

In  the  test  of  strains  of  Red  Rustproof  oats,  conducted  on  the 
same  field  in  1919,  adjoining  the  oats  variety  test,  the  same  variety 
was  used  as  check,  and  the  crop  was  seeded  on  the  same  day  with  the 
same  machine,  but  the  check  plots  were  in  every  sixth  instead  of  every 
ninth  plot.  The  corresponding  data  for  these  check  plots  are  given  in 
Table  21. 

Although  the  variability  of  these  plots  is  lower,  the  relative  va- 
riability of  plots  of  different  sizes  is  similar  to  that  of  the  variety  test. 
The  single  interior  rows  are  on  the  average  24  per  cent  more  variable 
than  the  3-row  block.  The  3-row  plot  is  only  very  slightly  more  va- 
riable than  the  5-row  plot. 


Experiments  in  Fiei.d  Plot  Technic 


47 


Table  21.— Y1E1.D  AND  Variabiuty  of  Check  Plots. 
Single-row,  Three-row,  and  Five-row.— Oats   Strain  Test  1919. 


Number 

Yield 

Size  of  plot 

of  plots 

per  acre 

Standard  deviation 

bu. 

bu. 

% 

Single-row 
Row  1 

18 

41.87 

6.35 

15.15 

Row  2 

18 

40.88 

5.52 

13.51 

Row  3 

18 

43.50 

5.81 

13.37 

Row  4 

18 

45.00 

7.31 

16.25 

Row  5 

18 

41.50 

6.37 

15.35 

Mean  of  three 

interior  rows 

18 

43.13 

6.21 

14.38 

Mean  of 

five  rows 

18 

42.55 

6.27 

14.73 

Three-row  Plot 
(Interior   rows) 

18 

43.13 

5.04 

11.68 

Five-row  Plot 

18 

42.55 

4.86 

11.41 

In  the  wheat  variety  test  of  1920  the  check  variety  was  Fultz, 
which  was  seeded  at  the  rate  of  six  pecks  per  acre  in  every 
seventh  plot.  The  results  of  interest  in  this  connection  are  shown  in 
Table  22. 


Tabi,e  22. — Y1E1.D  AND  Variability  of  Checks  PivOTs. 
Single-row,  Three-row,  and  Five-row. — ^Wheat  Variety  Test  1920 


Number 

Yield 

Size  of  plot 

of  plots 

per  acre 

Standard  deviation 

bu. 

bu. 

% 

Single-row 

Row  1 

80 

20.74 

6.58 

31.72 

Row  2 

80 

17.28 

5.02 

29.05 

Row  3 

80 

18.34 

4.50 « 

24.52 

Row  4 

80 

17.29 

5.10 

29.48 

Row  5 

80 

19.37 

6.00 

30.97 

Mean  of  three 

interior  rows 

80 

17.64 

4.87 

27.68 

Mean  of 

five  rows 

80 

18.60 

5.44 

29.15 

Three-row  Plot 

(Interior  rows) 

80 

17.64 

4.43 

25.11 

Five-row  Plot 

80 

18.63 

4.77 

25.60 

48 


Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 


Again  the  single  rows  are  distinctly  more  variable  than  the  3-row 
plot,  in  this  case  to  the  extent  of  10  per  cent.  The  5-row  and  the 
3-row  plots  are  about  equally  variable,  the  slight  advantage  in  this  case 
being  in  favor  of  the  latter. 

To  summarize,  it  is  evident  that  the  protected  3-row  plot  is  some- 
what less  subject  to  plot  variability  than  the  protected  single-row,  but 
the  relative  value  of  the  5-row  plot  harvested  entire  and  the  same  plot 
harvested  as  a  protected  3-row  block  is  not  clear.  Some  further 
comparison  of  these  two  methods  was  made  in  1921.  The  variability 
of  the  check  plots  in  both  the  wheat  and  oats  tests  was  computed  as 
protected  3-row  and  as  unprotected  5-row  plots.  In  the  wheat  tests 
the  check  variety  was  Poole,  seeded  at  5  pecks  per  acre  in  every 
seventh  plot  in  the  variety  test,  and  in  every  sixth  plot  in  the  mixture 
test.  In  the  oats  tests  the  check  variety  was  Kherson,  seeded  at  10 
pecks  per  acre  in  every  sixth  plot.    The  results  are  shown  in  Table  23. 


TabIvE  23.— Yiei^d  and  Variabiwty  of  Check  Plots. 
Three-row  and  Five-row.— Wheat  and  Oats  Tests,  1921. 


Number 

Yield 

Size  of  plot 

of  plots 

per  acre 

Standard  deviation 

bu. 

bu. 

% 

Wheat  Variety  Test 

Three-row  Plots 

80 

14.89 

2.16 

14.50 

(Interior  rows) 

Five-row   Plots 

80 

13.98 

1.90 

13.61 

Wheat  Mixture  Test 

Three-row  Plots 

30 

15.48 

3.25 

20.98 

(Interior  rows) 

Five-row  Plots 

30 

15.78 

3.55 

22.49 

Oats  Variety  and  Strain  Tests 

Three-row  Plots 

120 

37.95 

4.61 

12.15 

(Interior  rows) 

Five-row   Plots 

120 

38.37 

4.70 

12.25 

In  no  case  are  the  differences  very  great.  The  variability  of  3-row 
blocks  is  slightly  greater  in  the  mixture  test  and  that  of  5-row  blocks 
in  the  variety  test  of  wheat.  There  is  practically  no  difference  between 
the  two  in  the  oats  tests. 

Apparently  there  is  no  constant  material  gain  in  plot  uniformity 
obtained  by  the  inclusion  of  the  border  rows  of  the  5-row  plot,  even 
though  the  size  of  the  plot  is  materially  increased  by  this  procedure. 
Even  if  variability  were  decreased  by  their  inclusion,  the  practice  would 
be  of  doubtful  value  in  most  tests,  for  the  reasons  given  in  the  last 
section ;  but  with  practically  no  decrease  in  variability  there  is  left  no 


Experiments  in  Fiei.d  Plot  Technic  49 

reason  for  the  harvesting  of  these  rows.  They  are  not  wasted  because 
they  are  not  harvested,  for  they  serve  a  valuable  purpose;  the  waste 
would  be  involved  rather  in  harvesting  them,  for  the  added  labor  and 
expense  would  contribute  nothing  to  the  accuracy  of  the  experiment. 

Although  protected  3-row  plots  are  less  variable  than  protected 
single-row  plots,  they  are  not  necessarily  preferable.  Three  protected 
3-row  plots  require  the  same  area  as  five  protected  single-row  plots, 
and  the  harvesting  of  almost  twice  as  large  a  crop  (nine  rows  in  the 
first  case  for  every  five  in  the  second).  If  the  mean  yield  of  five 
single  rows  has  as  low  a  probable  error  as  the  mean  yield  of  three 
3-row  plots,  the  protected  single-row  plot  will  ordinarily  be  pre- 
ferable, because  of  the  reduction  of  labor  in  harvesting  and  thresh- 
ing. When  the  standard  deviation  of  the  check  plot  yields  is  known, 
the  probable  error  of  the  mean  of  any  number  of  replicate  plots  can 
be  computed  and  the  number  of  replications  for  any  given  degree  of 
accuracy  determined.  If  single-row  plots  were  29  per  cent  more 
variable  than  3-row  plots,  the  probable  errors  of  the  mean  of  three 
3-row  plots  and  of  five  single-row  plots  would  be  equal,  since  the  prob- 
able error  of  the  mean  is  equal  to  the  probable  error  of  a  single  deter- 
mination divided  by  the  square  root  of  the  number  of  determinations, 
and  since  the  square  root  of  5  is  29  per  cent  greater  than  the  square 
root  of  3.  In  the  cases  herein  cited  the  advantage  of  the  3-row  plots 
was  considerably  less  than  29  per  cent  in  every  case,  and  we  may  con- 
fidently expect  therefore  that  protected  single-row  plots  repeated  five 
times  will  be  less  variable  than  protected  three-row  plots  repeated  three 
times,  which  would  require  the  same  area  and  more  labor. 

Some  further  evidence  on  the  relative  variability  of  the  protected 
3-row  plot  and  the  unprotected  5-row  plot,  or,  in  other  words,  of 
5-row  plots,  harvested  with  and  without  their  border  rows,  may  be  ob- 
tained from  the  yields  of  the  tested  varieties  and  strains.  Since  the 
number  of  replications  of  each  strain  is  small,  average  deviations  are 
given  instead  of  standard  deviations.  The  inclusion  of  border  rows  in 
the  5-row  plots  should  not  increase  variability,  since  the  adjacent  va- 
rieties are  the  same  in  each  series,  and  the  competitive  effect  should  be 
no  more  variable  than  would  be  that  of  the  same  variety.  A  clear-cut 
comparison  of  5-row  and  3-row  plots  is  therfore  available  in  this  case. 
In  the  case  of  the  check  plots  this  comparison  was  somewhat  obscured 
by  the  competitive  eflFect  of  diflFerent  varieties  on  the  border  rows,  which 
might  be  expected  to  increase  variability  and  thus  to  conceal  a  possible 
advantage  of  the  5-row  plot. 

The  average  variability  of  3-row  and  5-row  plots  in  the  strains 
tested  in  these  experiments  is  shown  in  Table  24.     In  each  case  the 


50 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


figur,e  given  is  the  mean  of  the  average  variabilities  determined  for  all 
of  the  varieties  or  strains  in  the  experiment. 

Table  24. —  Yield  and  Variability  oe  Test  Plots. 
Three-row  and  Five-row. 


Season 

Number 
of  vari- 
eties 

Number 
of  Repli- 
cations 

Three-row  Plots 

Five-row    Plots 

Test 

Yield 

bu.  per 

acre 

Average 
Devia- 
tion 

% 

Yield 

bu.  per 

acre 

Aver- 

Devia- 
tion 
% 

Barley   varieties 

1919 

27 

3 

22.06 

15.35 

21.95 

15.44 

Oats    strains 

1919 

15 

50.07 

5.96 

50.20 

5.10 

Wheat  varieties 

1920 

96 

13.39 

24.27 

13.78 

24.36 

Wheat   varieties 

1921 

96 

15.42 

10.30 

15.57 

9.74 

Wheat  mixtures 

1921 

30 

17.62 

9.84 

18.15 

10.03 

Oats  varieties 

1921 

32 

29.85 

10.86 

30.70 

10.14 

Oats    strains 

1921 

64 

28.40 

10.82 

28.63 

10.58 

There  is  no  consistent  difference  in  variability  between  the  3-row 
plots  and  the  5-row  plots.  In  some  cases  the  former  are  more  va- 
riable; in  others  the  latter;  and  in  no  case  is  the  difference  in  varia- 
bility great.  These  results  are  contrary  to  the  general  impression  that 
variability  decreases  with  increase  in  size  of  plots.  Apparently,  in 
tests  of  this  kind,  the  3-row  plot  is  lar'ge  enough  to  give  a  fair  sample 
and  nothing  is  gained  by  adding  the  other  two  rows.  When  it  is  con- 
sidered that  the  addition  of  these  two  rows  undoubtedly  introduces 
systematic  error  from  competition  to  a  greater  or  less  extent,  and 
involves  a  very  considerable  increase  in  the  labor  of  harvesting  and 
threshing,  there  remains  little  doubt  that  the  border  rows  of  5-row 
plots  are  best  discarded  in  experiments  of  this  sort. 

Replication  of  Plots. — It  is  generally  considered  that  the  error 
from  soil  variability  may  be  reduced  to  any  desired  point  by  replica- 
tion in  sufficient  degree.  For  any  given  degree  of  precision  the  num- 
ber of  replications  required  is  dependent  on  the  variability  of  the 
replicate  plots.  When  every  plot  in  a  single-row  test  is  provided  with 
two  border  rows  the  area  required  for  the  test  is  tripled,  the  replicate 
plots  are  separated  more  widely,  and  variability  is  usually  increased, 
since  the  range  of  soil  variability  will  usually  be  greater  when  a  larger 
area  is  included. 

The  removal  of  border  effect  from  the  rows  harvested  for  yield 
may  in  some  cases  reduce  variability  more  than  enough  to  balance  this 
increase,  but  when  the  unprotected  single  rows  are  grown  in  the  same 
order  in  each  series,  variability  will  not  be  much  affected  by  competi- 
tion, as  before  stated.     Consequently  more  replications  of  single-row 


Experiments  in  Field  Plot  Technic 


51 


plots  protected  by  borders  than  of  the  single-row  plots  not  so  pro- 
tected may  actually  be  required  for  a  given  degree  of  plot  variability. 
Similarly,  more  replications  may  be  required  in  a  test  of  a  large  num- 
ber of  strains  than  in  a  test  of  a  small  number,  as  Montgomery"  has 
suggested. 

The  number  of  replications  required  may  be  determined  with  a 
fair  degree  of  accuracy  from  the  variability  of  the  check  plots.  The 
variability  of  the  check  plots  in  parts  of  the  large  fields  used  as  com- 
pared with  the  variability  of  the  check  plots  in  the  whole  fields  shows 
the  importance  of  this  point.    In  Table  25  are  given  the  standard  de- 

Table  25. — Relation  of  Plot  Variability  to  Size  of  Experiment  Field. 
Check  Plots  in  Wheat  Variety  Test  1930. 


No.  of 

Size  of  field 

Plots 

Yield 

Standard  deviation 

bu.  per  acre 

bu. 

% 

Four    ranges    (1st)* 

20 

14.79 

3.789 

25.62 

Four  ranges  (2nd) 

20 

18.35 

4.073 

22.20 

Four  ranges  (3rd) 

20 

16.67 

3.659 

21.94 

Four  ranges  (4th) 

20 

20.74 

3.876 

18.69 

Mean 

20 

17.64 

3.849 

22.11 

Eight  ranges  (1st) 

40 

16.57 

4.316 

26.05 

Eight  ranges  (2nd) 

40 

18.71 

4.285 

22.90 

Mean 

40 

17.64 

4.302 

24.48 

Sixteen  ranges 

80 

17.64 

4.430 

25.11 

♦The  four-range  and  eight-range  sections  are  in  order  from  west  to  east. 


I 


viations  of  the  yields  of  the  check  plots  in  the  wheat  variety  test  of 
1920.  The  yields  of  the  three  interior  rows  of  the  check  plots  were 
used  in  computing  these  constants. 

Twenty-four  varieties  could  have  been  replicated  four  times  in 
the  four  ranges  comprising  any  quarter  of  the  field.  As  the  probable 
error  of  a  single  plot  yield  is  14.92  per  cent  we  may  conclude  that  the 
probable  error  of  the  mean  of  four  such  yields  would  be  about  7.46 
per  cent.  But  when  96  varieties  must  be  tested,  as  they  were  in  this 
test,  four  replications  require  16  ranges,  and  the  probable  error  of  the 
mean  yield  becomes  8.47  per  cent.  A  degree  of  precision  which  could 
be  attained  with  four  replications  in  a  test  covering  four  ranges  could 
hardly  be  attained  with  five  replications  in  a  test  covering  sixteen 
ranges. 

Corresponding  data  for  the  wheat  variety  test  of  1921  are  given 
in  Table  26.  Although  the  variability  in  this  experiment  was  much 
lower,  the  relative  variability  of  large  and  small  experiment  fields  was 


52 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


Table  26. — Relation  of  Plot  Variability  to  Size  oe  Experiment  Field. 
Check  Plots  in  Wheat  Variety  Test  1921. 


No.  of 

Size  of  field 

Plots 

Yield 

Standard  Deviation 

bu.  per  acre 

bu. 

% 

Four  ranges  (1st)* 

16 

15.78 

1.584 

10.04 

Four  ranges  (2nd) 

16 

15.48 

1.586 

10.25 

Four  ranges  (3rd) 

16 

15.28 

2.099 

13.74 

Rour  ranges  (4th) 

16 

13.01 

2.091 

16.07 

Mean 

16 

14.89 

1.840 

12.53 

Eight  ranges  (1st) 

32 

15.63 

1.592 

10.19 

Eight  ranges  (2nd) 

32 

14.14 

2.383 

16.85 

Mean 

32 

14.89 

1.988 

13.52 

Sixteen  ranges 

64 

14.89 

2.159 

14.50 

♦The  four-range  and  eight-range  sections  are  in  order  from  west  to  east. 

similar.  Again  the  degree  of  accuracy  obtained  with  four  replications 
in  four  ranges  would  have  been  unattainable  with  five  replications  in 
16  ranges. 

The  oats  variety  test  and  strain  test  in  1921  were  contiguous,  oc- 
cupying 24  ranges,  with  120  check  plots  of  Kherson  oats,  or  one  in 
every  sixth  plot.    The  variability  of  these  check  plots  in  sections  of 


Table  27.— Relation  oe  Plot  Variability  to  Size  oe  Experiment  Field. 
Check  Plots  in  Oats  Variety  and  Strain  Test,  1921. 


No.  of 

Size  of  field 

plots 

Yield 

Standard  deviation 

bu.  per  acre 

bu. 

% 

Four  ranges  (1st) 

20 

35.81 

4.75 

13.26 

Four  ranges  (2nd) 

20 

34.95 

2.90 

8.30 

Four  ranges  (3rd) 

20 

38.14 

4.21 

11.04 

Four  ranges  (4th) 

20 

39.60 

4.66 

11.77 

Four  ranges  (5th) 

20 

38.91 

4.14 

10.65 

Four  ranges  (6th) 

20 

40.31 

4.14 

10.27 

Mean 

ZO 

37.95 

4.13 

10.88 

Eight  ranges  (1st) 

40 

35.38 

3.96 

11.19 

Eight  ranges  (2nd) 

40 

38.87 

4.50 

11.58 

Eight  ranges  (3rd) 

40 

39.60 

4.21 

10.62 

Mean 

40 

37.95 

4.22 

11.13 

Twelve  ranges  (1st) 

60 

36.30 

4.25 

11.71 

Twelve  ranges  (2nd) 

60 

39.60 

4.36 

11.01 

Mean 

60 

37.95 

4.31 

11.36 

Twenty-four  ranges 

120 

37.95 

4.61 

12.15 

Experiments  in  Field  Plot  Technic  53 

four,  eight,  and  twelve  ranges,  and  in  the  whole  field  of  24  ranges,  is 
shown  in  Table  27. 

The  variability  of  the  whole  field  of  24  ranges  was  12  per  cent 
greater  than  the  average  variability  of  sections  of  four  ranges  each. 
In  this  case  again,  five  replications  in  the  larger  field  would  have  given 
less  accurate  results  than  four  replications  in  the  smaller. 

In  each  of  the  cases  cited  above  a  steady  increase  in  variability 
is  apparent  as  the  size  of  the  experiment  field  is  increased.  It  is  obvious 
that  the  substitution  of  3-row  plots  with  discarded  borders  for  single 
rows  will  result  in  greater  variability,  and  will  require  increased  rep- 
lication for  the  same  degree  of  accuracy. 

From  the  foregoing  statements  it  will  be  clear  that  the  number  of 
replications  necessary  for  a  given  degree  of  accuracy  may  vary  con- 
siderably with  conditions.  The  number  to  be  used  in  any  specific  ex- 
periment should  be  determined  from  the  variability  of  the  field  in 
question  and  the  degree  of  accuracy  required.  The  variability  of  the 
check  plots  is  usually  considered  a  measure  of  the  variability  of  the 
field.  But  when  the  number  of  replications  to  be  used  or  the  extent  of 
experimental  error  is  determined  from  the  variability  of  the  check 
plots,  it  is  assumed  that  the  variability  of  different  varieties  of  the  same 
crop  is  approximately  the  same  under  the  same  conditions.  This  of 
course  is  not  strictly  true.  The  yield  of  two  varieties  may  be  deter- 
mined by  very  different  factors,  as  has  been  stated,  and  their  relative 
variability  may  also  be  quite  different.     The  variability  of  120  plots 


Table  28.— Son,  Heterogeneity  oe  an  Experiment  Field  as  Determined  From 

Yields  of  Two  Check  Varieties. 

Oats  Variety  and  Strain  Tests.   1921. 

Number  Average  Probable  error  of  a 

Check  variety         of  plots      yield    Standard  deviation    single  yield  determination 

bu.  bu.  %  bu.  % 

Kherson  120  37.95  4.61  12.15  3.11  8.20 

Red  Rustproof  120  22.44  3.99  17.78  2.69  11.99 


each  of  Kherson  and  Red  Rustproof  oats,  grown  side  by  side  as  check 
plots  in  the  oats  variety  and  strain  test  of  1921,  illustrate  the  possibil- 
ity of  a  serious  error  in  the  use  of  the  standard  deviation  of  check 
plots  as  a  measure  of  the  variability  of  an  experiment  field.  These 
determinations  are  shown  in  Table  28. 

The  field  would  have  been  considered  decidedly  less  variable  if 
Kherson  had  been  used  as  the  check  variety  than  if  Red  Rustproof  had 


54  Missouri  Agr.  Exp.  Sta.  Research  Bui<letin  49 

been  used.  Both  of  these  are  standard  recommended  varieties  for  the 
region,  though  they  differ  decidedly  in  their  characteristics.  Both 
have  been  used  frequently  as  check  varieties  at  the  Missouri  station  in 
past  seasons.  From  the  variability  of  the  Kherson  check  plots  the  mean 
yield  of  four  replicate  plots  in  this  experiment  would  be  considered 
to  have  a  probable  error  of  4.10  per  cent ;  from  the  Red  Rustproof  plots 
the  same  determination  would  be  given  a  probable  error  of  6.00  per 
cent.  A  degree  of  precision  for  which  we  would  assume  four  replica- 
tions necessary,  judging  from  the  Kherson  check,  would  require  nine 
replications  according  to  the  yields  of  the  Red  Rustproof  check. 

The  importance  of  choosing  a  check  variety  typical  of  the  va- 
rieties tested,  if  its  variability  is  to  be  considered  a  criterion  of  the 
variability  of  the  field,  is  obvious.  Whether  it  is  possble  to  choose 
a  "typical  variety"  for  the  purpose,  in  the  case  of  ordinary  variety 
tests,  remains  to  be  seen. 

ADJUSTMENT  OF  YIELDS  BY  MEANS  OF  CHECK  PLOTS 

Adjustment  of  plot  yields  by  the  use  of  check  plots  has  been  a 
common  practice  in  field  experiments  during  recent  years.  It  is 
recognized  that  no  experiment  field  is  perfectly  uniform  in  produc- 
tivity, and  the  attempt  is  made,  by  means  of  the  check  plot  adjustment, 
to  compensate  the  varieties  or  treatments  which  chance  to  be  located 
on  the  less  productive  plots  for  the  resulting  loss  in  yield.  The  com- 
mon method,  in  variety  tests,  is  to  distribute  over  the  field,  as  fre- 
quently as  practicable,  check  plots  planted  to  the  same  variety  and 
similarly  handled  in  every  way.  The  variation  in  yield  among  these 
check  plots  is  then  considered  a  measure  of  the  productivity  of  the 
soil.  By  various  methods,  differing  only  in  detail,  the  yields  of  the 
test  plots  in  parts  of  the  field  giving  high  check  yields  are  reduced,  and 
those  of  test  plots  in  parts  giving  low  check  yields  are  increased,  in 
proportion  to  the  productivity  of  the  soil,  as  indicated  by  the  yields 
of  neighboring  check  plots. 

Previous  Investigation. — Several  investigations  of  the  effect  of 
such  adjustment  on  the  variability  of  replicate  plots  have  been  re- 
ported. The  majority  of  these  have  been  conducted  in  connection  with 
experiments  of  the  type  discussed  in  the  preceding  section,  in  which 
uniformly  handled  fields  have  been  harvested  in  small  sections.  Cer- 
tain of  these  sections,  or  plots,  have  been  considered  check  plots,  and 
on  the  basis  of  their  yields  the  yields  of  the  remaining  plots  have  been 


EXPKRIME^NTS  IN  FlELD  PlOT  TeCHNIC  55 

adjusted.  The  reduction  of  variability  of  the  adjusted  plot  yields  is 
the  measure  of  the  efficiency  of  the  method. 

Morgan"  reports  an  experiment  of  this  sort,  in  which  63  plots, 
planted  first  to  wheat  and  then  to  fodder  corn,  in  the  same  season, 
were  used.  The  variability  of  the  plot  yields  was  steadily  reduced  as 
the  number  of  check  plots  was  increased. 

In  a  similar  experiment  reported  by  Lyon",  in  which  37  replicate 
1/100  acre  plots  of  corn  were  harvested,  the  use  of  checks  in  every 
second  or  third  plot  was  found  to  reduce  variability,  but  they  were  of 
little  value  when  farther  apart. 

Montgomery"  states  that  alternating  check  plots  with  test  plots 
gives  a  high  degree  of  accuracy,  but  the  total  number  of  plots  required 
when  this  method  is  used  is  greater  than  when  the  same  degree  of  ac- 
curacy is  attained  by  the  use  of  replication. 

Kiesselbach"  reports  a  comprehensive  trial  of  three  methods  of 
adjusting  yields  by  means  of  check  plots  in  a  uniform  field  of  207 
1/30-acre  plots  of  Kherson  oats.  The  effect  on  plot  variability  is  shown 
in  Table  29. 

Table  29. — Effect  on  Pi.ot  Variabiuty  of  Adjusting  Yields  by  Check 
Plots  (Kiesselbach). 

Coefficient 
Method  of  of  variability 

adjustment  Actual  Adjusted 

yields  yields 

Alternate  check  plots. 
Correction  based  on 
average  of  two  ad- 
jacent checks  7.85  7.01 

Checks  every  third  plot. 
Correction  based  on  one 
adjacent  check  plot  7.79  7.35 

Checks  every  third  plot. 
Correction  by  progres- 
sive method,  based  on 
two  nearest  checks  7.87  6.57 


From  these  results  Kiesselbach  concludes  "The  yield  of  system- 
atically distributed  check  plats  cannot  be  regarded  as  a  reliable  meas- 
ure for  correcting  and  ^establishing  correct  theoretical  or  normal 
yields  for  the  intervening  plats." 

It  should  be  noted  at  this  point  that  even  if  adjustment  by  check 
yields  were  found  invariably  effective  in  experiments  of  this  sort, 


56  Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 

its  value  in  ordinary  variety  testing  would  not  be  definitely  estab- 
lished. The  practice  involves  not  only  the  assumption  that  the  yields 
of  the  check  plots  are  a  fair  indication  of  the  productivity  of  the  in- 
tervening plots  for  the  check  variety,  but  the  further  assumption  that 
different  varieties  respond  similarly  to  differing  growing  conditions. 
Adjustment  of  yields  should  therefore  give  better  results  in  such  ex- 
periments as  those  cited  above  than  it  could  be  expected  to  give  in 
actual  variety  tests. 

This  point  is  well  illustrated  by  observations  reported  by  Salmon". 
Two  varieties  of  barley,  Gatami  and  Odessa,  were  grown  side  by  side 
in  fiftieth-acre  plots  in  five  distributed  portions  of  a  field.  Gatami  gave 
an  average  yield  of  18.3  bushels  per  acre,  with  quite  uniform  yields  in 
the  five  plots,  as  evidenced  by  their  probable  error  of  0.68  bushel, 
while  Odessa  yielded  13.3  bushels  per  acre  in  the  first  plot,  6.35  bushels 
per  acre  in  the  second,  and  a  negligible  yield  in  the  other  three.  Ob- 
viously the  adjustment  of  the  yield  of  either  of  these  varieties  on  the 
basis  of  the  other  variety  as  a  check,  would  enormously  increase 
rather  than  decrease  the  experimental  error.  As  Salmon  points  out, 
an  error  similar  in  kind  though  less  in  degree  may  occur  commonly 
in  variety  tests,  when  the  yields  of  varieties  are  determined  by  dif- 
ferent limiting  factors.  And  if  this  is  generally  the  case,  adjustment 
by  check  yields  will  be  of  doubtful  value,  even  if  it  were  found  to 
eliminate  variability  completely  in  uniform  plot  tests. 

There  is  a  growing  tendency,  consequently,  to  discontinue  the  use 
of  check  plots  for  adjusting  yields  in  variety  tests,  and  to  use  them 
only  to  measure  soil  variability  and  to  indicate  the  degree  of  error 
in  yield  determinations  of  the  tested  varieties.  Adjustment  of  yields 
has  never  been  as  common  in  preliminary  tests  as  in  tests  on  larger 
plots,  principally  because  of  the  great  amount  of  computation  neces- 
sary in  adjusting  the  yields  of  ten  or  twenty  replicate  rod-rows  of  a 
large  number  of  varieties,  and  because  the  yield  of  a  single  rod-row, 
exposed  to  varying  competition  and  materially  affected  by  small  me- 
chanical errors,  is  at  best  a  very  unreliable  measure  of  productivity  on 
which  to  base  the  adjustment  of  the  yields  of  several  other  plots. 

Experimental  Results. — It  would  of  course  be  very  desirable  to 
use  check  plots  for  reducing  plot  variability,  if  the  method  could  be 
relied  on,  because  of  the  economy  of  the  practice.  The  only  certain 
method  of  reducing  plot  variability  is  by  means  of  replication,  and  it 
may  be  considered  a  fairly  general  rule  that  the  variability  of  plots 
on  a  given  field,  as  measured  by  the  standard  deviation  or  the  prob- 
able error,  will  in  general  be  reduced  by  replication  in  proportion  to 
the  square  root  of  the  number  of  replications.     In  other  words,  the 


Experiments  in  Field  Plot  Technic  57 

variability  of  the  mean  of  16  replicate  plots  will  be  about  half  that  of 
the  mean  of  4  replicate  plots.  Now  the  maximum  use  of  check  plots, 
that  is,  the  practice  of  alternating  check  plots  and  test  plots,  requires 
the  same  land  and  labor  as  would  be  required  by  doubling  the  num- 
ber of  replications,  if  no  check  plots  were  used.  As  doubling  the 
number  of  replications  will  in  general  give  a  standard  deviation  about 
equal  to  the  original  standard  deviation  divided  by  the  square  root  of 

2,  it  will  reduce  variability  about  30  %  (——  =7071  J .  If  alternat- 
ing with  check  plots  will  consistently  reduce  variability  more  than  30 
per  cent  it  will  be  generally  a  more  economical  way  to  control  error. 
Similarly,  the  use  of  check  plots  in  every  third  plot  requires  as  much 
land  as  would  be  required  by  increasing  the  number  of  replications  by 
50  per  cent  (using  three  replications  instead  of  two,  or  fifteen  instead 
of  ten).  From  this  relation  the  reduction  of  variability  necessary  if 
this  practice  is  to  equal  replication  in  effectiveness  can  be  easily  com- 
puted. Such  determinations  for  check  plots  at  various  intervals  are 
shown  in  Table  30. 

Tabi^e;  30.— Reduction  of  Variabiuty  by  the  Use  of  Check  Plots  EquivaIvEnt 

TO  That  Probably  Attainable  With  the  Same  Number 

OF  Plots  by  Replication. 


Reduction  in 

standard  deviation  to 

Distribution  of 

Equivalent  increase  in 

be  expected  by  such 

check  plots 

number  of  replications 

increase  in  replication 

% 

% 

Alternate  plots 

100.00 

29.29 

Every  third  plot 

50.00 

18.35 

Every  fourth  plot 

33.33 

13.50 

Every  fifth  plot 

25.00 

10.55 

Every  sixth  plot 

20.00 

8.71 

Every  seventh  plot 

16.67 

7.41 

Every  eighth  plot 

14.29 

6.47 

Every  ninth  plot 

12.50 

5.75 

Every  tenth  plot 

11.11 

5.12 

If  protected  single-row  or  3-row  plots  are  used  in  preliminary 
experiments  a  more  reliable  measure  of  soil  productivity  is  available, 
and  consequently  the  adjustment  of  yields  is  more  likely  to  be  of  value, 
than  when  unprotected  single-row  plots  are  used.  By  the  use  of 
planting  plans  of  the  sort  employed  in  these  experiments,  it  is  pos- 


58  Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 

sible  to  adjust  the  yields  by  a  somewhat  shortened  method.  If  adjust- 
ment of  yield  is  eflfective  in  reducing  plot  variability  in  this  sort  of 
test  it  can  be  accomplished  with  but  little  increase  in  labor.  In  each 
of  the  tests  reported  in  this  paper  a  trial  of  the  effectiveness  of  adjust- 
ing yields  by  means  of  check  plots  was  made,  the  criterion  of  accuracy 
being  in  each  case  the  variability  of  the  yields  of  the  replicate  plots  of 
each  variety.  Since  the  number  of  replicate  plots  was  only  three 
or  four  the  average  deviation  was  determined  instead  of  the  stand- 
ard deviation. 

Method  Used  in  Adjusting  Yields. — The  method  employed  in  ad- 
justing yields  may  be  described  as  follows:  The  average  yield  of  all 
check  plots  and  the  relative  yield  of  each  check  plot  in  terms  of  this 
average  (that  is,  the  quotient  obtained  by  dividing  the  yield  of  the  in- 
dividual check  plot  by  the  average  yield  of  all  check  plots)  were  de- 
termined. The  relative  yield  of  each  check  plot,  expressed  in  per- 
centage of  the  mean  check  yield,  is  designated  hereafter  as  the  "plot 
value"  of  that  check  plot.  When  the  average  yield  of  all  check  plots 
is  25  bushels  per  acre,  the  plot  value  of  a  check  plot  yielding  30  bushels 
per  acre  is  120  per  cent — in  other  words  it  is  20  per  cent  more  pro- 
ductive than  the  average.  Now  assuming  gradual  change  in  the  pro- 
ductivity of  the  soil  between  check  plots,  each  test  plot  is  assigned  a 
plot  value  by  interpolation.  The  adjusted  yield  of  each  plot  is  then 
determined  by  dividing  the  actual  yield  by  the  plot  value. 

The  short  method  for  adjusting  yields,  referred  to  above,  is 
based  on  the  fact  that  the  varieties  occur  in  the  same  order  in  each 
series.  Thus  in  the  field  diagrammed  in  figure  1,  the  following  se- 
quence of  plots  occurs  in  each  of  the  four  series : 

ck      1      17      33      49      65      81      ck 

Now  if  the  average  yield  of  the  four  check  plots  adjoining  variety 
1,  and  the  average  yield  of  the  four  check  plots  adjoining  variety  81 
are  each  given  a  plot  value,  corresponding  plot  values  for  the  mean 
yields  of  varieties  1,  17,  33,  49,  65,  and  81  may  be  interpolated,  and 
the  mean  yields  may  be  adjusted  in  one  operation.  The  same  method 
may  be  used,  of  course,  regardless  of  the  number  of  replications.  The 
result  will  not  be  exactly  the  same  as  that  of  averaging  the  adjusted 
yields  determined  individually,  but  will  in  most  cases  approximate  it 
closely,  the  slight  difference  being  caused  by  the  disproportion  of  yield 
and  plot  value  in  the  plots  averaged.  It  is  doubtful  that  either  meth- 
od is  consistently  more  accurate  than  the  other. 

When  the  check  plot  yield  is  used  in  the  adjustment  of  the  yields 
of  other  plots  it  is  of  course  essential  that  it  should  be  a  reliable  de- 
termination, not  unduly  affected  by  factors  not  affecting  the  neighbor- 


Experiments  in  Fikld  Plot  Technic 


59 


ing  plots.  For  example  if  the  yield  of  a  check  plot  is  reduced  20  per 
cent  by  a  poor  stand,  the  adjusted  yields  of  neighboring  plots  will  be 
increased  to  the  same  extent  as  if  the  check  plot  yield  had  been  low  be- 
cause of  poor  soil,  and  will  consequently  be  considerably  higher  than 
they  should  be.  It  is  important  therefore  that  conditions  be  made  as  fa- 
vorable as  possible  for  accurate  yield  testing  when  this  method  is  used. 
One  cause  for  poor  results  in  the  adjustment  of  yield  in  some  of  the 
experiments  reported  in  this  paper  was  failure  to  protect  the  outside 
strip  of  check  plots  by  means  of  border  rows,  in  a  few  of  the  tests,  be- 


TaBIvE    31.— REIvATIVE    VARIABII.ITY    OF    AcTUAI,    AND    ADJUSTED    YiElvDS. 

Average  Deviation  in  Percentage  of  Yield. — Barley  Variety  Test  1919. 


Average 

deviation 

Planting 

Actual  yields 

Adjusted  yields 

number 

Variety                   3  interior  rows 

5  rows    3  interior  rows 

5  rows 

% 

% 

% 

% 

1 

Hanna  906 

19.81 

17.82 

13.15 

10.80 

3 

Steigum  907 

15.17 

18.79 

13.48 

8.40 

3 

Luth  908 

29.97 

28.17 

5.51 

4.62 

4 

Eagle  913 

26.14 

29.79 

9.71 

12.98 

6 

Servian  915 

18.37 

17.97 

7.36 

5.59 

7 

Odessa  916 

2.31 

4.33 

23.99 

17.01 

8 

Lion  923 

14.65 

12.10 

11.37 

11.03 

10 

Horn  926 

4.08 

2.00 

16.45 

12.74 

11 

Odessa  927 

13.62 

9.16 

21.62 

13.76 

12 

Summit  929 

6.28 

6.45 

14.23 

11.59 

13 

Mariout  932 

11.02 

11.57 

18.68 

14.31 

14 

Odessa  934 

13.73 

13.91 

11.18 

10.31 

15 

Peruvian  935 

13.25 

17.87 

12.42 

16.82 

16 

Trebi  936 

11.27 

12.53 

18.78 

18.28 

18 

Oderbrucker  940 

10.77 

14.46 

13.60 

15.98 

19 

Prankish  953 

20.53 

19.65 

22.63 

18.49 

20 

Manchuria  956 

6.88 

6.33 

13.89 

10.68 

21 

Oderbrucker  957 

17.88 

13.62 

1.97 

3.27 

22 

Manchuria  x  Champion 
of  Vermont 

39.47 

39.19 

21.93 

20.35 

23 

Luth  972 

16.77 

18.61 

7.05 

7.48 

24 

Red  River  973 

13.94 

11.02 

12.37 

12.33 

25 

Featherston  1118 

21.40 

20.89 

8.47 

13.39 

26 

Featherston  1119 

16.59 

15.25 

4.78 

12.26 

27 

Featherston  1120 

15.91 

13.64 

2.48 

6.44 

28 

Hanna  x  Champion 
of  Vermont  1121 

16.00 

16.81 

28.36 

28.50 

29 

Manchuria  1125 

6.79 

14.42 

7.78 

1.55 

30 

Malting  1129 

12.86 

10.40 

5.40 

9.02 

Mean 

15.35 

15.44 

12.91 

12.15 

60 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


cause  of  lack  of  space.  The  check  plots  growing  on  the  border  of  the 
field  were  materially  reduced  in  yield,  in  some  cases,  notably  the  oats 
strain  test  of  1919  and  the  wheat  variety  test  of  1921.  In  these  cases 
the  variability  of  the  actual  and  adjusted  yields  has  been  computed 
both  for  all  series  and  for  the  remaining  series  when  the  one  affected 
by  an  unreliable  check  is  discarded. 

Relative  Variability  of  Actual  and  Adjusted  Yields. — The  relative 
variability  of  actual  and  adjusted  yields  of  both  3-row  and  5-row  plots 
in  the  barley  variety  test  is  shown  in  Table  31.  In  this  test  there  were 
three  replications,  and  the  check  variety  was  Oderbrucker,  in  every 


Tabi,e  32. — REi^ATivie  Variabii^ity  of  Actuai,  and  Adjusted  Yiei^ds. 

Average  Deviation  in  Percentage  of  Yield 

Oats  Variety  Test  1919. 


Average 

Deviation 

Planting 

3  Series 

4  Series 

number 

Variety 

(3  interior  rows) 

(3  interior  rows) 

Actual 

Adjusted 

Actual 

Adjusted 

yields 

yields 

yields 

yields 

% 

% 

% 

% 

1 

A.  sterilis  nigra 

4.32 

1.46 

9.18 

5.02 

2 

Black  Mesdag 

9.03 

9.69 

7.29 

12.90 

3 

C.  I.  602 

13.72 

16.00 

16.30 

13.63 

3 

C.  I.  603 

4.72 

3.09 

5.84 

3.88 

5 

C.  I.  620 

4.73 

10.14 

11.24 

13.67 

6 

Early  Champion 

18.63 

15.18 

14.97 

14.65 

7 

Early  Gothland 

14.20 

4.67 

11.55 

4.18 

8 

Garton  473 

5.99 

6.25 

8.42 

9.42 

9 

Garton  585 

14.08 

19.44 

16.92 

19.95 

10 

Golden  Giant 

9.44 

14.31 

14.40 

15.09 

11 

Irish  Victor 

9.69 

3.29 

7.72 

16.40 

12 

Japanese  Selection 

6.87 

4.71 

11.85 

5.20 

13 

June 

18.37 

11.19 

17.53 

10.37 

14 

Kherson  Selection 

17.01 

9.20 

15.06 

20.36 

15 

Fulghum 

9.69 

11.36 

13.06 

17.32 

16 

Lincoln 

21.07 

12.54 

16.56 

11.83 

17 

Monarch 

6.12 

4.55 

9.06 

33.36 

18 

North  Finnish 

8.69 

5.17 

7.84 

27.03 

19 

Scottish  Chief 

5.05 

4.28 

5.10 

15.42 

20 

Sparrow  bill  (Missouri) 

10.98 

10.82 

12.38 

13.15 

21 

Sparrow  bill    (Cornell) 

4.45 

3.25 

12.11 

3.85 

22 

Tobolsk   1 

6.17 

3.85 

13.92 

5.38 

23 

Tobolsk  2 

11.56 

9.24 

20.35 

13.96 

24 

White  Tartar 

10.94 

4.75 

9.51 

4.54 

Mean 

10.23 

8.27 

12.01 

12.94 

ExPKRIMEiNTS  IN  FlELD  PlOT  TECHNIC 


61 


sixth  plot.  As  a  result  of  the  adjustment  of  yields,  the  average  devia- 
tion of  3-row  plots  was  reduced  from  15.35  per  cent  to  12.91  per  cent, 
a  reduction  of  16  per  cent,  and  that  of  5-row  plots  from  15.44  per 
cent  to  12.15  per  cent,  a  reduction  of  21  per  cent. 

The  relative  variability  of  actual  and  adjusted  yields  in  the  oats 
variety  test  of  1919  is  shown  in  Table  32.  In  this  field  the  check. 
Red  Rustproof,  was  in  every  ninth  plot.  When  the  series  affected  by 
the  faulty  check  yields  of  the  border  plots  is  included  the  variability  of 
the  adjusted  yields  is  slightly  higher  than  that  of  the  actual  yields, 
but  when  this  series  is  discarded  the  average  variability  as  measured 
by  the  mean  deviation  is  reduced  19  per  cent. 

It  might  be  expected  that  the  oats  strains  grown  on  the  same  field 
would  show  a  greater  reduction  of  variability  than  the  varieties,  since 
practically  all  of  them  were  of  the  same  variety  as  the  check,  and  since 

Tabu  33.— Relative  Variability  of  Actual  and  Adjusted  Yields. 

Average  Deviation  in  Percentage  of  Yield. 

Oats  Strains  Test  1919. 


Planting      Accession 
number        number 


Average  deviation 
Actual  yields  Adjusted  yields 

interior  rows     5  rows    3  interior  rows    5  rows 
%  %  %  % 


1 

0119 

10.30 

7.75 

11.22 

8.81 

2 

0120 

4.70 

6.58 

3.01 

1.76 

3 

0121* 

6.76 

3.25 

4.57 

4.14 

4 

0122 

4.62 

3.52 

6.46 

3.82 

5 

0123 

9.91 

8.25 

11.47 

9.62 

6 

0125 

3.18 

3.34 

5.39 

6.60 

7 

0126 

7.62 

5.95 

10.56 

16.58 

8 

0127* 

6.76 

5.09 

6.92 

9.85 

9 

0124* 

6.13 

6.34 

4.92 

4.59 

10 

0133 

7.07 

4.77 

3.92 

5.36 

11 

0128 

4.17 

3.56 

3.58 

3.36 

12 

0129 

5.02 

7.07 

5.94 

6.35 

13 

0130 

4.20 

2.62 

6.74 

9.72 

14 

0131 

2.59 

2.59 

4.98 

2.94 

15 

0132 

7.38 

5.81 

12.38 

12.08 

Mean 

5.96 

5.10 

6.80 

7.04 

*  Not  taxonomically  Red  Rustproof. 


the  check  plots  were  more  frequent,  being  in  every  sixth  plot.  The 
results  of  adjusting  yields  in  this  test,  both  for  protected  3-row  plots 
and  for  unprotected  5-row  plots  in  four  series  are  shown  in  Table  33. 
Contrary  to  expectation,  the  variability  was  not  reduced  by  adjustment 


62 


sli 


•5  s  S  „« 


So     >, 


II 


2^ 


t:^ 


o  S3  C 

><3      o 


bo  V. 

rt  g 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


O^0*■♦«nCS^0^fOt^1r0^t>^«>01^>.^O^00^«>v0C^JO^r0lOCT\VOOM■O^C^80^J^»^xO00vnv0TJ■, 


■*oooOt^jr> 


I 


9vtnTj-,-itxOO^'-)'^CV|OvOvO'^000'^OOoOvOOt^tx\OrOVOt^>nM<-iOtncMtnoOOTHOrHroC<a-<4-<^0\C^)t-v 


T^^»^O^vO^O00^0^^O^.-^^0^«.^«.T^\0(^^rHV00^<^\0<NC^Jf0O^a3TtM 


iOlf»5f^P0^.-iC>JC>».-<CQM^f*>' 


iM^irn-i.-ir-i^.-i,-»,-i.-iCqroCVlr-irq. 


,-lC^^»-c»-lr-l,-lC^«N.-l.-t        p 


i-iWr»5CSlf^.-iCMC>J<NOJ<Mf^<-Hr'5i-i         ,-ii-i„»oPJra»-iOJ.-ir^.-<rtCarOCvi>-irqrH.-(CNCSI>-<C\Ji-ir-i,-i^,-i<MrH,-t      <! 

) 

^  >n  0\  rt  '-' 


o  d  o  d  o 

t-i   U   ti   U   t-i  CM 

V  V  V  i;  Vfo 

§§§§§^ 
^^^^^^ 

C  C  C  C  C  o 

sag)  Si  s>^  £ 


.'->  'V 


9a 


vOOOOOOOOOOOOo 

t)1->cv^cv^c^^cMc^^c^c^^cv|CM^^c^^c^^ 


V   V   V  <:«  V   V 


t2iIdk;ji:jk;3.i?L:?'"  "^  OOOoni-«4J<uti454JOO u 

SSSSS!?;?;;?  OOhP^IIh^^PM  rtPilP^rtrtrtrtrt  C/3Cnc/3C/3C/3C«C/5C/5c/3C«C«C«a)H 


CM        ^ 

d^§ 


>»N 


o      a_ 


't«cqovdo6c5^o6o\vovoo6u^^o\a\c4cNi'*OTt^'c5Tto6o\'**'^osoN'^^cMa\vd»o.-Ic>w^ 


CM  rH  M  rO  .-•  rH  , 


fOO\tnlOrOfOOO^^tnpoOO 


,_|^,-t^         C4  f-l  O)  C<)  C>«  M  l-<  rl  f-l 


eaMcsiT-i.-i.-ic«c<j«-<' 


tn^o^•*•-;\ot>>cM»-^a\oo^«.Ocslt-Jt>.lnc^I^<.^oCMo^^^oo^looqoocM^xfo  ^.  ^^*n 

rr}inuioo<r>r^»o.4o>cMCMr>CModfor^ioodiovo.-<csii-HO\o\'-i'-^''-<CMvo^^  ♦til 

i-l  T-4  C^  1-1  C>4        »-<  »-4  CM  CM  CM  <M  •-•  •-<  M  r-l  ^  ^  rH        CM  C^  OJ  i-H  i-H  ,-i  »0  tO  »-•  ^  i-n-l  •*   T 


OfOVOOfOTJ■oOO»-<00^<.0\rorJ•^oCMOOOO^Ou^fCWO^O»«O^O^T^^O■*C^JCMO^f^C^NO•^ 

r^NdooNOso6Tfro'^cMrf.-^oc5o6r<I\ooo6c>avodo6t^Tj-os'4-ON«^»-^a\o6^c5c>oscM^ 

MOl'f^CMCMrg— iMOJ.-iCM»-litfO"«t-'-<'OC<J'*CMCM<NCMCMfOi-i        .-ipjC>JCMCM«NlCM<»»fOfOCS>OlrO'*roOlf«0fOCMW»»; 


00O00.-^^0C«>00l«0^C^^CM^01-^O'-<««0^»O^»^00CM,-^t^.•*O^^O0^CM•«t'*•*f^l«00 
CM^<I^'c^^^<J^'TfT^^«Io^^OlOOvO^>I"^^>I•^^OO^OO^pr>\Or-<O^CM'*'o^»«^>^C^ 


CM  CM  ■*  ««  M  C«J  CM  ' 


CM'-<mi^oo 

.-•  00  00  00  CNJ  CM 

d  d  d  d  d  d 

"^  rS  "2  "o  !2  r2 


it-iCM»HTtf^-*^CMCv|'*CMCMCMCMCM'*t->i-i'-ii-'CMCMCM<-"CM'*CMf^<-<CMCM^fO«-i»OfOCM 


TSOOvOCMO  00'<trt 

goTj-t^oo  ooo 

=  ftrt  i-4^  *^^  I'Tv    /^fc  (-^ 


CM  01 

°-  s 


o 
>. 


5.S3 


•si 


00     ^  ooooooo  o  o, 

PufJcccccccccccgcgfJ 
wwbcbobciscbfibobobcbcbc  bc.^f.SJM.ffJ 


»3  0.;2  X  J3  J3  J:  J3  J3  J3  X  J3  J=  J3  •?  J5 . 

'*^.H.y.ii.y.y.y.-.y.y.y-H-"-y- 


I  CM  fO  ■*  ">  ^  t^  I 


0\O»HCM^0'*>OV0r^00O\©T-iCMf^'*-»5^«iJ 
CMfOWrofOrofOPO'orofO^'*'*^'*'*^^' 


Experiments  in  Field  Plot  Technic  63 

of  yield.  A  possible  explanation  is  the  extremely  low  variability  of  the 
actual  yields,  indicating  that  the  field,  which  was  quite  small,  was  re- 
latively uniform.  Any  gain  in  uniformity  from  a  check  adjustment 
of  yields  would  of  course  be  expected  to  be  greater  in  highly  variable 
than  in  more  uniform  fields.  The  relative  uniformity  of  this  field 
is  indicated  not  only  by  the  low  mean  deviation  of  the  test  plots,  but 
also  by  the  low  standard  deviation  of  the  check  plots,  which  was  only 
11.68  per  cent,  as  compared  with  a  standard  deviation  of  22.59  per 
cent  in  the  check  plots  of  the  adjoining  oats  variety  test. 

The  effect  of  adjusting  yields  on  the  variability  of  3-row  and 
5-row  plots  in  the  wheat  variety  test  of  1920  is  shown  in  Table  34. 
In  this  test  the  check  variety,  Fultz,  was  grown  in  every  sevetith  plot. 
There  were  four  series  of  the  ninety-six  varieties. 

The  reduction  in  variability  was  very  marked,  being  37  per  cent 
for  3-row  plots  and  42  per  cent  for  5-row  plots.  The  variability  of 
almost  every  variety  was  reduced,  and  the  reliability  of  the  results 
was  undoubtedly  much  increased. 

The  wheat  variety  test  of  1921,  occupying  an  equal  area  on  a 
neighboring  field,  and  with  similar  varieties  and  the  same  planting 
plan,  gave  decidedly  diflFerent  results.  In  this  field  the  check  va- 
riety was  Poole.  Several  check  plots  on  the  border  were  abnormal, 
and  the  computations  are  therefore  given  both  for  three  series  and  for 
four,  the  series  affected  by  the  abnormal  check  yields  being  dis- 
carded in  the  former  case.  The  relative  variability  of  actual  and  ad- 
justed yields  is  shown  in  Table  35. 

Although  the  check  yields  are  somewhat  less  variable  for  three 
series  than  for  four,  the  adjustment  was  not  effective  in  either  case  in 
reducing  variability.  The  adjusted  yields  are  10  per  cent  more  va- 
riable than  the  actual  yields  for  the  three  series  and  34  per  cent  higher 
for  the  four. 

Similar  results  were  obtained  in  the  wheat  mixture  test  of  the 
same  season,  in  which  several  of  the  same  varieties  were  included, 
and  the  same  check  variety  was  used.  In  this  test  the  check  variety 
was  in  every  sixth  plot,  and  four  replications  were  used.  The  results 
of  adjusting  yields  are  shown  in  Table  36.  Variability  was  increased 
from  9.84  per  cent  to  13.81  per  cent,  an  increase  of  40  per  cent.  Thus 
the  results  of  adjusting  yields  of  wheat  varieties  in  1921  are  directly 
contrary  to  the  results  of  the  same  practice  in  1920. 

Difference  in  Results  Obtained  by  Adjustment  with  Different 
Check  Varieties. — In  the  oats  variety  and  strain  tests  of  1921,  two 
check  varieties,  Kherson  and  Red  Rustproof,  were  grown.  In  these 
tests  96  strains  were  included,  32  of  Kherson,  32  of  Red  Rustproof,  and 


64 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


.1  .sg^ 


S5      p-S 


.:;'o 


<2 


ic<io\Ooot^cqoot^forj-t^oo 


Trlt^^^-H^^»^c«^\ooo^v\nooooo^pot^p^>n^«^o\voc^^c>^t«ooT^fo^x'*;0\c^>c<^^-^o^\qcgc^^oo^li^«^ 
o6^^odvo^>I■^o^Ol-3o6c^^•*o^««c>^«I^^f^o6o^o^^^^•*^>^■'-^lWo6u^l-^■^o^es>^-< 


ONO^^»nO\>0«OC»J»-ivnC>JOOf^OsOOOOO\OOioO\rJ-ir)roO'^iOT}-t^O\vOTfO»0\OvOOt^OOOO»-HVOOOr^      u» 

o^csJO■<*■c<^o^^rOl-<T^ooa^oo^t^^T^ooo^^^^o^lnt^^-^^^tr>^^Tl-lnoo^•^"^c^ln^ooo^o^fou^^oooc^^  ^ 

r-<        ,-1  ,-1  _rt^        MCS|<-i        CMCMtM  .-1        ,-1  »-i  .-I        ^        rt  rt        o)  •-<  fi  1-1  .-I       t^ 


c« 

> 

.efe 


0^  a 


.2    .S  §^ 


^^2 

.a 


V      2  w  -, 


O  O  1-1 1«  OS  <-■  »-i 

fo  Ti- Tj- lo  o  — <  csj 

^  ,-1  rH  f-H  CS]  O)  CM 

d  d  d  d  d  d  d 

Uil-.biV<WiW>Wi^ 

T3  TJ  "O  "a  "O  73  •«  fjj 
C  C  C  C  C  C  Cc>4 
O  O  O  O  O  O  OrH       13 

acccccco     g    oa 

be  be  bo  be  bo  bo  bc^  Jjm 
xlcx'^^lSla  fe  bo    ^ii 
oooouyog  UiTS  O  O 


gc3: 


Ti-  rt 


7    O    I-  ' 

O  O  o 


'o'o'o 
o  o  o 


(S^^PlH 


'00 

■  4;  a>  o 


Q'Sm 


^OCS^vO.-lfOt^^»«00»nCMOt^^^O®««^^-l1-lO\•*':2^^0^fOPOO\0\»noOOOT^VOvOOOO^^O^t^O^C^^»OO^VO 
0\t>.tOOOs<*5t^\0'*vO»-'CMOO^HOr^vo»-«\o\0'*i*Oior»50JC>air}vOOvOO\PQ»-'<N'*«Oi-iroOOCsit*5VOi-i 


eNi»^cgvdcNJvd\d»>Ii>.'ir>o6vdo6t>Io.-iin«iic5vd' 


^^o\^opoo\o\»nooooT^vovoooo^^o^t^o^c^^»oo^voooo^•«tc>^ 

i«-0»or»5<Ne^iovOOvOO\CQ»-'<N'*«Oi-iroOOCsit*5VOi-iiOintoa\0\ 

uioOi-Jt-Ifor^oioor^IoocsicooooNTfOTttNliiiooooovoinfoi-I^^ 

CN],-I^TH  ,-lrt  rH  rl  CSl  r-l  M  -1  CSI -t  ,-1  ,-1 

C<«iOVOCSIOCqvOTl-cq^OTt.-ir^vOO\t^m^Ot^OOOOrc.-iO\00\0\\Oi-noo\OsOOvO»-"rotntvOJVOOOCMOmOsrgtN 
^0^^^00O^^O^0O^«00O^00^•-lVOt^t^1-^^0^00•*C<l^-J'-<■*_Ov0Ot^.■0\0q^^00■*li^lnrH^^.0000^«.|>.1-< 

u^o6lna^•^to»oo6c5fo^dvdcvi^odoo6vd1-^^do\^d•^c>c^^^d^d^Ntotno6^>^lnu^^^ 


if>OOOOOnrOQsOO»nO\0\»/100VOOOvOfO-*rOl^mOOstxONtvMMO 
■^di>>V0iO\0'<*i-i'*CMOior»^vO»-iOr0t^0)ON<O>O0000«-<00Or»50\OM-'0\O 


io6^t^vno\o6<*io6o6oj'^o«-lo6ovdotoo6^ot>^t>^ir> 


p^J^^oovoooooT^^.-^•*T^lrJvooo■*.-l0^ooo^ovo»i^^<.c>J1-^vo^-.•-^o^<^•-;pc>^u>oo 


» 


o  eg  c 


feK- 


I  00  so  «M  O  •<1- P^ 
5o-<l-t^00O 
JoOOOOvOsO  c 
^  ro  CO  <~0  fO  ■*   O 

^ 


<-i  iuOTc/>cn<n(0(nio<A  jQ 


t^ooti 


O   O    L. 


S  so2^ 

.J5      ■<j-oOcsiio»noo"^-'»^ 


^55 


d  d  d  d  d  d  d  d  d 


o 

•5    u 


a;   V   X  T3  ID  73  t3  T3  T5  "O  T3 13 -d 

oBCPppcoooooooooo 

'oSS 


^bi,£22cccccsccccocS2 

»Hc^^^o•*»o^or^ooo^o»HC^^^O'*u1^or^ooo^O'-'^^'^•*»«vo^»ooc^o.-^N<*>•*w^^ot^ooc^o»HC3«25lnvot^oo 


Expe;rimknts  in  Fiki.d  Plot  Technic 


65 


Table.  36— Relative  Variability  oe  Actual  and  Adjusted  Yields. 
Average  Deviation  in  Percentage  of  Yield.  Wheat  Mixture  Test  1921 


Average  Deviation 

Planting 

Actual  yields 

Adjusted  yields 

number 

Variety 

(3  interior 
rows) 

(3  interior 
rows) 

1 

Fulcaster 

9.67 

16.90 

2 

Harvest  Queen 

9.35 

21.47 

3 

Mixture  No.  1 

6.12 

20.11 

4 

Michigan  Wonder 

7.88 

20.51 

5 

Nigger 

2.33 

20.16 

6 

Michigan  Wonder  No. 

31 

4.93 

13.86 

7 

Michigan  Wonder  No. 

54 

12.96 

16.03 

8 

Mixture  No.  2 

15.38 

17.86 

9 

Michigan  Wonder  No. 

96 

4.99 

13.88 

10 

Michigan  Wonder  No. 

209 

5.30 

14.83 

11 

Beechwood  Hybrid  No. 

12 

9.04 

11.01 

12 

Beechwood  Hybrid  No 

85 

14.98 

15.49 

13 

Mixture  No.  3. 

16.76 

10.47 

14 

Beechwood  Hybrid  No 

.  87 

10.16 

11.94 

15 

Beechwood  Hybrid  No 

207 

20.80 

11.81 

16 

Michigan  Wonder  No. 

221 

7.13 

8.90 

17 

Kanred 

10.09 

12.86 

18 

Mixture  No.  4 

10.39 

8.44 

19  • 

New  York  123-32 

16.73 

12.09 

20 

Red  Rock 

14.04 

10.68 

21 

Red  Hussar 

12.71 

17.42 

22 

Turkey  (Kansas) 

17.32 

13.74 

23 

Mixture  No.  5 

2.87 

12.73 

24 

Michigan  Amber 

3.39 

10.71 

25 

Nigger 

4.09 

10.47 

26 

Fulcaster  (Co-op) 

2.09 

14.25 

27 

Fulcaster  (Outl) 

11.97 

17.18 

28 

Mixture  No.  6 

11.19 

7.75 

29 

Fulcaster  (B lazier) 

11.41 

6.77 

30 

Fulcaster  (Cowles) 

9.09 

14.11 

Mean 

9.84 

13.81 

32  of  other  varieties.  The  yields  w^ere  adjusted  by  means  of  each 
check  variety  separately,  to  determine  the  relation  between  the  ef- 
fectiveness of  yield  adjustment  and  the  similarity  of  the  check  to  the 
tested  variety.  The  results  of  this  adjustment  on  plot  variability  are 
shown  in  Tables  37  and  38. 

The  variability  of  the  yields  of  the  Red  Rustproof  strains  was 
somewhat  reduced  (6  per  cent)  by  adjustment  according  to  the  yields 


66 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


TabIvE  37, — Relative  Variability  of  Actual  and  Adjusted  Yields. 
Average  Deviation  in  Percentage  of  Yield.     Oats  Variety  Test  1921 


Average  deviation 

Planting 

Actual  yields 

Adjusted  yields 

number 

Variety 

(3  interior 

(3  interior 

•  rows) 

rows) 

(Kherson)   (Red  Rustproof) 

% 

% 

% 

65 

Burt 

10.22 

11.54 

11.00 

66 

Canadian 

9.29 

8.93 

18.37 

67 

C.  I.  603 

9.31 

4.94 

13.89 

68 

Culberson 

6.46 

8.80 

4.44 

69 

Danish  Island 

10.53 

8.83 

12.56 

70 

Early  Dakota 

9.33 

7.96 

11.45 

71 

Early  Gothland 

10.00 

19.16 

14.69 

72 

Carton  748 

14.35 

13.26 

14.77 

73 

Green  Russian 

9.75 

11.23 

13.75 

74 

Irish  Victor 

9.43 

8.07 

15.99 

75 

Joanette 

30.75 

29.36 

26.94 

76 

Fulghum  042 

5.19 

8.50 

8.99 

77 

Monarch 

4.76 

6.36 

8.54 

78 

Monarch  Selection 

2.89 

5.74 

11.55 

79 

Scottish  Chief 

10.95 

15.01 

8.66 

80 

Silvermine  050 

11.24 

9.88 

9.21 

81 

Silvermine  Selection 

11.25 

16.14 

3.16 

82 

Sparrowbill  (C) 

23.93 

23.03 

25.23 

83 

Sterilis  Selection 

8.02 

7.30 

9.17 

84 

Storm  King 

11.68 

13.94 

13.15 

85 

Swedish  Select  057 

14.48 

14.89 

11.80 

86 

Fulghum  065 

8.81 

11.04 

9.41 

87 

Fulghum  0113 

22.19 

11.18 

15.85 

88 

Silvermine  0115 

8.38 

6.29 

3.59 

89 

Silvermine  0117 

6.90 

8.95 

9.69 

90 

Fulghum  0124 

5.17 

3.38 

7.89 

91 

Fulghum  0145 

9.81 

8.63 

15.66 

92 

Fulghum  0149 

10.19 

10.77 

15.70 

93 

Fulghum  0151 

10.85 

12.71 

10.80 

94 

Fulghum  0152 

9.07 

14.59 

19.61 

95 

Silvermine   0165 

5.63 

11.32 

4.62 

96 

Swedish  Select  0165 

16.74 

14.02 

8.74 

Mean 

10.86 

11.43 

12.15 

of  the  Red  Rustproof  check,  but  was  slightly  increased  (2  per  cent) 
when  the  Kherson  check  was  used.  On  the  other  hand,  the  variability 
of  the  yields  of  the  Kherson  strains,  though  not  reduced  by  either  check, 
was  increased  only  4  per  cent  by  the  Kherson  check,  while  it  was  in- 
creased 48  per  cent  by  the  Red  Rustproof  check.  Neither  check  was 
effective  in  adjusting  the  yields  of  the  other  varieties,  the  Kherson 


Experiments  in  Field  Plot  Technic 


67 


Table  38. — Rei^ative  VariabiIvITy  of  Actuai.  and  Adjusted  Yiei^ds. 
Average  Deviation  in  Percentage  of  Yield. — Oats  Strain  Test  1921 
(Red  Rustproof  and  Kherson) 


Red 

Rustproof 

strains 

Kherson  strains 

Strain 

Average   deviation 

i 

Strain 

Average   deviation 

1 

s 

tn     • 

.11 

^^2 

Adjusted 
(3   interioi 

yields 
•   rows) 

.H  ' 

Adjusted    yields 
(3   interior  rows) 

be 

1-2 

bfi 

3  2 

IS 

C 

(Kher. 
son) . . 

(Red 
Rust- 
proof) 

(Kher- 
son) . . 

(Red 
Rust- 
proof) 

% 

% 

% 

% 

% 

% 

1 

066 

18.13 

15.48 

13,04 

2 

023 

15.80 

7.59 

12.93 

3 

067 

12.89 

14.19 

11.36 

4 

040 

3.86 

5.59 

10.45 

5 

068 

23.14 

21.34 

12.47 

6 

041 

9.50 

5.82 

4.07 

7 

069 

21.55 

20.54 

11.70 

8 

052 

3.46 

2.83 

10.49 

9 

072 

14.29 

12.26 

10.34 

10 

053 

6.26 

5.97 

10.14 

11 

074 

12.18 

17.23 

13.94 

12 

079 

11.49 

9.91 

10.20 

13 

075 

13.40 

18.28 

18.80 

14 

080 

1.72 

7.02 

13.20 

15 

0118 

28.77 

32.06 

26.92 

16 

082 

6.19 

8.74 

15.01 

18 

0119 

10.32 

13.47 

13.62 

17 

083 

5.31 

5.88 

9.26 

20 

0120 

7.28 

6.11 

12.32 

•    19 

085 

8.69 

10.65 

7.30 

22 

0122 

17.16 

12.32 

14.20 

21 

086 

11.73 

7.45 

8.45 

24 

0125 

10.91 

11.52 

8.40 

23      Mixture***    4.87 

3.84 

9.19 

26 

0126 

10.41 

10.24 

4.66 

25 

088** 

13.04 

13.79 

9.16 

28 

0128 

14.48 

17.36 

2.76 

27 

089 

4.69 

6.77 

12.89 

30 

0129 

7.89 

6.31 

7.44 

29 

090 

2.84 

4.85 

10.64 

32 

0130 

7.99 

11.78 

9.17 

31 

091 

12.46 

14.67 

10.84 

33 

0131 

12.43 

13.96 

13.23 

34 

094 

4.59 

6.43 

6.57 

35 

0132 

17.77 

14.67 

12.11 

36 

095 

4.36 

4.96 

14.62 

37 

0133 

14.07 

11.63 

13.55 

38 

096 

4.39 

7.71 

4.66 

39 

0134 

29.91 

30.37 

29.50 

40 

097 

5.53 

6.97 

11.80 

41 

0135 

14.36 

17.58 

13.11 

42 

098 

9.09 

10.03 

13.18 

43 

0136* 

7.80 

7.59 

12.69 

44 

099 

6.89 

6.26 

10.20 

45 

0141 

12.58 

13.30 

11.11 

46 

0100 

6.90 

4.65 

8.55 

47 

0163 

2.70 

1.82 

14.28 

48 

0155 

12.75 

4.49 

23.56 

50 

0169 

21.95 

17.79 

23.03 

49 

0157 

6.34 

7.40 

14.18 

52 

0181 

9.95 

7.62 

9.69 

51 

0158 

10.81 

12.24 

6.26 

54 

0182 

26.12 

21.76 

20.84 

53 

0159 

6.33 

10.82 

8.26 

56 

0183* 

4.52 

5.51 

8.99 

55 

0160 

4.98 

6.12 

12.52 

58 

0383 

10.10 

15.60 

20.18 

57 

0161 

5.55 

9.19 

9.27 

60 

0391 

9.55 

11,37 

6.47 

59 

0162 

11.28 

13.38 

9.47 

62 

0394 

13.03 

11.52 

10.29 

61 

0167 

2.65 

3.37 

4.41 

64 

0395 

8.69 

11.40 

17.96 

63 

0174 

10.74 

8.96 

15.67 

M 

ean 

14.47 

14.70 

13:55 

Mean 

7.16 

7.44 

10.59 

*  Not  taxonomically  Red  Rustproof.     Excluded  from  average. 
**  Not   taxonomically    Kherson.      Excluded    from    average. 
***Mixture  of  strains   082,   094,   0100,    0174. 

check  increasing  their  variabiHty  7  per  cent,  and  the  Red  Rustproof 
check  20  per  cent.  These  results  indicate  the  importance  of  using 
a  check  variety  typical  of  the  varieties  tested,  when  adjustment  of 
yields  is  to  be  made ;  and  the  danger  of  increasing  rather  than  decreas- 


68 


Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 


ing  error  by  this  practice  when  the  tested  varieties  are  quite  different 
in  habit  from  the  check  variety. 

The  use  of  an  unsuitable  check  variety  not  only  increases  the 
margin  of  error,  but  it  may  cause  very  deceptive  comparative  results. 
For  example,  the  average  yields  of  the  Kherson  strains  0155  and  0157, 
unadjusted  and  adjusted  according  to  the  yields  of  both  check  va- 
rieties, are  shown  below: 


Strain 

Method 

0155 

0157 

Yield 

Average 
Deviation 

Yield 

Average 
Deviation 

Unadjusted 

Adjusted  by  Kherson  check 

Adjusted  by  Red  Rustproof  check 

37.50 
34.50 
39.94 

12.75 

4.49 

23.56 

43.69 
43.69 
39.38 

6.34 

7.40 

14.18 

The  17  per  cent  advantage  in  yield  of  strain  0157  is  increased  to 
27  per  cent  by  the  Kherson  adjustment,  and  since  the  variability  of 
the  replicate  yields  is  reduced  by  the  adjustment  we  may  fairly  as- 
sume that  the  latter  is  the  more  reliable  figure.  But  when  the  Red 
Rustproof  check  is  used  for  adjusting  yields,  the  advantage  of  strain 
0157  disappears  entirely.  The  inaccuracy  of  the  yields  adjusted  by 
Red  Rustproof  is  indicated  by  the  increase  in  plot  variability  result- 
ing from  this  adjustment.  Thus  the  adjustment  of  yields  by  means 
of  check  plots  may  mask  considerable  differences  in  yields  between  the 
varieties  under  test. 

Although  Kherson  and  Red  Rustproof  are  decidedly  different  in 
type,  both  are  commonly  grown  in  Missouri,  and  both  have  been  used 
frequently  here  as  check  varieties  in  oats  variety  tests.    It  is  interesting 


Tabi,e  39.— REI.ATIVE  Variability  of  Actual  and  Adjusted  Yields  oe  Kherson 

AND  Red  Rustproof  Oats,  Each  in  120  Distributed  Plots. 

Oats  Variety  and  Strain  Tests  1921. 


Variety 

Kherson 

Red  Rustproof 


Yield 
Actual    Adjusted 

Standard  deviation 
Actual      Adjusted 
yield         yield 
%             % 

37.95           39.04 
22.44           22.80 

12.15 

17.78 

20.79 
19.92 

EXPEJRIMKNTS  IN  FiE:LD  PloT  TitCHNiC 


69 


to  determine  the  effect  on  variability  of  adjusting  the  yields  of  the 
120  plots  of  Kherson,  on  the  basis  of  those  of  the  120  plots  of  Red 
Rustproof  adjoining  them,  and  those  of  the  120  plots  of  Red  Rustproof, 
on  the  basis  of  the  yields  of  the  adjoining  Kherson  plots.  In  this 
adjustment  the  yield  of  each  plot  is  divided  by  the  plot  value  of  the 
adjoining  plot,  and  the  method  corresponds  to  method  II  used  by 
Kiesselbach  in  the  experiment  cited  above  (see  Table  29).  The  results 
of  the  yield  adjustment  are  shown  in  Table  39. 

The  adjustment  of  plot  yields  by  means  of  check  plots  of  a  va- 
riety distinctly  different  in  type  resulted  in  a  decided  increase  in  plot 
variability,  even  though  the  plot  values  used  were  determined  in  each 
case  by  the  yield  of  the  immediately  adjacent  plot.  If  the  yields 
of  the  Kherson  and  the  Red  Rustproof  plots  had  been  perfectly  ac- 
curate measures  of  the  productivity  of  the  soil,  the  plot  values  of  the 
adjacent  plots  would  have  been  almost  the  same  in  each  of  the  120 
locations,  and  the  adjustment  of  the  yields  of  either  variety  by  those 
of  the  other  would  have  reduced  variability  almost  to  zero.  Instead, 
variability  was  actually  and  very  decidedly  increased,  because  the  sec- 
tions of  the  field  which  gave  relatively  high  yields  of  Kherson,  gave 
relatively  low  yields  of  Red  Rustproof,  and  vice  versa,  in  many  cases. 
In  fact,  there  was  very  little  relation  between  the  productivity  of  a 
portion  of  the  field  as  determined  by  a  Kherson  check,  and  the  pro- 


tH 

o 

wo 
rH 

o 
o 

g 

o 

CO 

2 

§ 

o 

8 

o 

CO 

o 

o 

g 

w 

o 

B 

B 

o 

B 

B 

B 

O 

B 

B 

B 

B 

o 

B 

o 

70 

tH 

o 

r-t 

o 

r-{ 

1H 

o 

1 

o 

o 

O 

o 

o 

o 

H 

60  to 

1 

1 

70  to 

80 

1 

1 

1 

3 

80  to 

90 

1 

1 

1 

1 

1 

1 

6 

90  to 

100 

2 

4 

1 

1 

1 

1 

10 

100  to 

110 

1 

2 

2 

2 

4 

3 

2 

3 

1 

20 

110  to 

120 

1 

1 

4 

3 

2 

2 

2 

2 

1 

18 

120  to 

130 

1 

3 

4 

1 

4 

4 

2 

3 

22 

130  to 

140 

1 

5 

1 

2 

3 

3 

1 

1 

1 

1 

19 

140  to 

150 

1 

1 

1 

3 

2 

2 

1 

11 

150  to 

160 

2 

2 

4 

160  to 

170 

1 

2 

1 

1 

5 

170  to 

180 
otal 

1 

^ 

T 

1 

2 

4 

2 

10 

20 

11 

20 

19 

16 

9 

3 

2 

0 

1 

120 

Figure  7.— Correi^atign  Between  Yields  of  Kherson  Check  Plots  and 
Yields  op  Adjacent  Red  Rustproof  Check  Plots,  in  Oats  Variety  and 
Strain  Tests  1921. 

r=     -f-.162  ±     .060. 


70 


Missouri  Agr.  Exp.  Sta.  Research  Bui^letin  49 


ductivity  of  the  same  portion  of  the  field  as  determined  by  an  adjacent 
Red  Rustproof  check  plot.  This  correlation  is  shown  in  figure  7.  The 
coefficient  of  correlation  is  less  than  three  times  its  probable  error — 
the  correlation  has  not  even  statistical  significance !  The  relative  pro- 
ductivity of  different  portions  of  the  field,  as  indicated  by  the  two  check 
varieties,  is  shown  in  figure  8.    If  Kherson  had  been  used  as  a  check 


Figure  8. — Rei^ative  Variabii^ity  of  Dieferent  Parts  of  an  Experiment 

F1EI.D,    AS    INDICATED    BY    THE    YlEWS    OF    ADJACENT    ChECK    Pi,OTS    OF    KhERSON 

AND  Red  Rustproof  Oats.  Oats  Variety  and  Strain  Tests  1921.  In  the 
diagram  on  the  left,  points  of  equal  productivity,  as  indicated  by  the  yields 
of  the  Kherson  check  plots,  are  connected  by  lines  (as  points  of  equal  elevation 
are  connected  by  lines  on  a  contour  map).  In  the  diagram  on  the  right,  the 
same  field  is  similarly  mapped  according  to  the  yields  of  the  Red  Rustproof 
check  plots.    The  numbers  indicate  the  plot  values  of  the  points  concerned. 

variety  for  adjusting  yields,  the  yields  of  certain  plots  would  have  been 
increased  to  compensate  for  the  low  productivity  of  the  soil;  if  Red 
Rustproof  had  been  used  the  yields  of  the  same  plots  would  have 
been  decreased  to  compensate  for  the  high  productivity  of  the  same 
soil.  The  fact  is  that  certain  parts  of  the  field  were  actually  more 
productive  than  the  average  for  Kherson  oats  and  less  productive  for 
Red  Rustproof,  as  is  indicated  by  the  fact  that  each  variety  of  check 
was  considerably  more  effective  in  the  adjustment  of  the  yields  of 
strains  of  the  same  variety  than  of  strains  of  the  other.  But  neither 
check  was  a  very  accurate  measure  of  the  productivity  of  the  soil, 
even  for  its  own  variety,  as  indicated  by  the  failure  of  adjustment  to 
reduce  variability  consistently  even  when  Kherson  strains  were  ad- 


Experiments  in  Fiei^d  Plot  Technic 


71 


justed  according  to  the  Kherson  check  and  Red  Rustproof   strains 
according  to  the  Red  Rustproof  check. 

Value  and  Limitations  of  Adjusting  Yields  by  Mewns  of  Check 
Plots. — The  effect  on  plots  variability  of  adjusting  yields  by  means  of 
check  plots  in  all  of  the  tests  is  shown  in  summary  form  in  Table  40. 
The  variability  of  the  test  plots  was  reduced  by  adjustment  in  three 
tests  and  was  increased  in  the  other  five.  It  is  noteworthy  that  the 
three  tests  in  which  plot  variability  was  reduced  by  adjustment  were 
characterized  by  high  plot  variability,  as  indicated  by  the  standard 
deviation  of  check  plots,  while  the  tests  in  which  adjustment  -was  not 

Table  40.— Summary  of  Relative  Variability  of  Actual  and  Adjusted 
Yields  of  Interior  Rows  in  All  Tests. 


Number 

Number 

Average 

deviation 

Test 

Season 

of  var- 

or  rep- 

Actual 

Adjusted 

eties  or 

lica- 

yields 

yields 

strains 

tions 

% 

% 

Barley  Variety 

1919 

27 

3 

15.35 

12.91 

Oats  Variety 

1919 

24 

3 

10.23 

8.27 

Oats  Strain 

1919 

15 

4 

5.96 

6.80 

Wheat  Variety 

1920 

94 

4 

24.27 

15.32 

Wheat  Variety 

1921 

94 

3 

10.45 

11.52 

Wheat  Mixture 

1921 

30 

4 

9.84 

13.81 

Oats  Variety 

1921 

32 

4 

10.86 

11.43* 

Oats  Strain 

1921 

64 

4 

10.82 

11.07* 

♦Adjustment  by  Kherson  check. 

effective  were  in  general  low  in  plot  variability.  In  1919  adjustment 
was  quite  effective  in  reducing  variability  in  the  oats  variety  test,  while 
it  increased  variability  in  the  oats  strain  test,  which  was  conducted  on 
the  same  field  and  similarly  handled  in  every  way.  In  fact,  conditions 
were  considered  more  favorable  for  the  effectiveness  of  the  practice 
in  the  strain  test  than  in  the  variety  test,  for  the  check  plots  were  closer 
together  and  12  of  the  15  strains  tested  were  taxonomically  identical 
with  the  check.  But  the  standard  deviation  of  check  plots  on  the 
part  of  the  field  on  which  varieties  were  grown  was  almost  twice  as 
great  as  on  the  part  of  the  field  on  which  the  strains  were  grown.  Ap- 
parently the  high  variability  of  the  plots  in  the  variety  test  was  caused 
in  large  part  by  differences  in  actual  soil  productivity  which  were 
largely  counteracted  by  the  adjustment  of  yields,  while  there  was 
little  variation  in  soil  productivity  in  the  strain  test  and  such  plot 
variability  as  occurred  was  largely  due  to  other  factors.  In  general 
therefore  the  adjustment  of  yields  will  probably  be  found  more  ef- 


72  Missouri  Agr.  Exp.  Sta.  Re:search  Bui^letin  49 

fective  on  fields  highly  variable  in  soil  productivity  than  on  more 
uniform  fields,  and  for  similar  reasons  the  method  will  probably  be 
found  more  effective  in  tests  covering  a  rather  large  area  than  in  tests 
covering  a  smaller  area. 

It  is  clear  that  the  adjustment  of  yields  by  means  of  check  plots 
entails  several  serious  disadvantages,  and  may  increase  experimental 
error  considerably.  Not  only  is  the  yield  of  the  check  plot  a  far  from 
perfect  measure  of  soil  productivity  for  the  check  variety,  but  the  pro- 
ductivity of  the  same  soil  for  other  varieties  may  be  decidedly  dif- 
ferent. The  method  is  therefore  more  effective  in  tests  of  strains  of 
the  same  variety  as  the  check,  than  in  tests  of  different  varieties.  When 
the  yields  of  check  plots  are  materially  affected  by  factors  not  similarly 
affecting  the  neighboring  test  plots,  adjustment  of  yields  will  increase 
experimental  error.  The  check  plots  must  therefore  be  effectively 
protected  from  competition,  border  effect,  mechanical  errors,  and  the 
like.  Moreover,  it  is  to  be  expected  that  the  effectiveness  of  adjusting 
yields  will  vary  with  the  season,  since  the  relative  influence  of  soil 
productivity  on  yield  varies  with  the  season.  For  example,  in  a  season 
in  which  winter  injury  is  exceptionally  severe,  actual  soil  fertility  may 
have  comparatively  Httle  to  do  with  plot  yields.  Now,  if  the  check 
variety  is  hardy,  its  yields  may  vary  with  the  soil  fertility,  but  when 
corresponding  adjustments  are  made  on  the  yields  of  tested  varieties 
limited  in  yield  by  winter  injury,  a  decrease  in  the  variability  of  repli- 
cate plots  is  hardly  to  be  expected.  The  same  considerations  apply 
of  course  to  yields  limited  by  many  other  factors. 

But,  although  a  multitude  of  objections  may  be  made  to  the 
theoretical  bases  of  the  practice  of  adjusting  yields  in  variety  tests, 
and  although  in  many  cases  it  undoubtedly  results  in  an  increase  rather 
than  a  decrease  in  experimental  error,  the  practice  offers  promise  of 
value  and  is  worthy  of  further  investigation.  The  effectiveness  of 
the  adjustment  of  yields  in  the  wheat  variety  test  of  1920,  in  which 
the  variability  of  replicate  test  plots  was  reduced  about  40  per  cent, 
is  a  demonstration  of  the  possibilities  of  the  method.  An  increase  in 
replication  of  plots  involving  the  same  increase  in  land  and  labor  would 
probably  have  reduced  plot  variability  only  about  7  per  cent.  A  thor- 
ough knowledge  of  the  value  and  limitations  of  yield-adjustment  by 
means  of  check  plots  might  enable  us  to  reduce  variability,  at  least  in 
some  types  of  plot  tests,  much  more  effectively  by  this  means  than 
by  replication.  The  saving  in  area  required  is  of  particular  significance 
in  preliminary  tests  if  border  rows  must  be  used  for  the  elimination 
of  competition,  since  in  this  case  the  area  required  for  a  large  number 
of  replications  is  in  many  cases  prohibitive. 


Expe:rime:nts  in  FieivD  Plot  Tejchnic  73 


CONCLUDING  REMARKS 

The  best  method  for  preliminary  variety  testing  is  one  which  will 
permit  the  accurate  determination  of  the  relative  value  of  the  va- 
rieties under  field  conditions,  with  the  use  of  a  small  area  of  land  for 
each  variety.  Some  precision  must  be  sacrificed  to  save  land,  and  in 
so  far  as  the  errors  involved  are  of  such  nature  that  their  extent  can 
be  approximately  determined,  and  conclusions  drawn  accordingly,  this 
sacrifice  of  precision  is  permissible.  In  many  cases  it  is  advisable,  for 
example,  to  reduce  the  number  of  replications  and  to  increase  the  least 
difference  in  yield  regarded  significant  to  a  sufficient  degree  to  com- 
pensate for  the  decrease  in  precision. 

But  these  considerations  do  not  apply  to  systematic  errors,  which, 
since  they  affect  the  yields  of  replicate  plots  similarly,  and  consequently 
have  little  effect  on  plot  variability,  cannot  be  accurately  measured. 
Typical  systematic  errors  commonly  involved  in  preliminary  testing 
are  (1)  modification  of  growing  conditions  favoring  some  varieties 
more  than  others,  such  as  hand  planting  or  wide  spacing  between  rows, 
and  (2)  competition  between  varieties  of  different  type,  resulting  from 
the  use  of  single-row  plots.  The  relative  value  of  varieties  under 
such  conditions  may  be  vastly  different  from  their  relative  value  un- 
der typical  field  conditions.  Even  should  measurable  experimental 
error  be  reduced  to  the  absolute  minimum,  such  a  variety  test  might 
give  results  entirely  misleading.  The  error  cannot  be  counteracted, 
as  can  non-systematic  errors,  by  increasing  the  least  difference  con- 
sidered significant,  nor  can  the  extent  of  error  of  this  sort  be  measured 
or  estimated  by  a  study  of  the  experimental  results. 

Systematic  error  must  therefore  be  reduced  by  every  practicable 
means.  Growing  conditions  in  the  preliminary  test  should  be  made  as 
similar  to  ordinary  field  conditions  as  possible.  The  effect  of  varietal 
competition  must  be  reduced  to  the  minimum.  If  this  can  be  ac- 
complished without  increasing  the  size  of  plots,  it  is  desirable  to  do 
so.  On  the  other  hand,  if  larger  plots  are  necessary  for  the  control 
of  competition,  larger  plots  should  be  used.  If  the  area  to  be  used 
for  preliminary  testing  cannot  be  correspondingly  increased,  the  num- 
ber of  replications  can  be  reduced  sufficiently  to  permit  the  use  of 
the  larger  plots  required  on  the  area  available.  This  will  necessitate 
a  decrease  in  the  degree  of  precision  of  the  test,  and  will  reduce  the 
rapidity  of  elimination  of  the  less  valuable  varieties.  But  is  it  not 
better  to  eliminate  the  undesirable  varieties  slowly  than  to  risk  the 
elimination  of  desirable  ones  by  a  more  rapid  analysis? 


74  Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 

The  error  from  competition  is  greater  when  different  varieties 
are  compared  than  when  different  strains  of  the  same  variety  are 
compared,  and  the  extent  of  error  is  roughly  in  proportion  to  the  de- 
gree of  difference  in  type  of  the  varieties  tested.  Competition  was 
not  found  to  be  correlated  closely  enough  with  earliness  of  heading, 
earliness  of  maturity,  height,  or  grain-straw  ratio  in  these  experi- 
ments to  permit  its  control  by  grouping  varieties  in  respect  to  these 
characters.  The  factor  found  most  closely  correlated  with  competitive 
value  was  yield,  but  the  correlation  even  in  this  case  was  not  close 
enough  to  permit  of  effective  control  by  grouping  varieties.  Moreover, 
it  would  be  impossible  in  practice  to  group  varieties  with  regard  to 
yield,  since  the  relative  yield  of  varieties  varies  so  widely  with  the 
season.  The  variety  expected  to  yield  poorly  is  not  ordinarily  included 
in  the  variety  test. 

When  different  strains  of  the  same  variety  are  grown,  the  error 
from  competition,  in  some  cases  at  least,  may  be  slight  enough  to 
justify  the  use  of  single-row  plots.  However,  competition  in  such 
cases  is  not  wholly  absent,  and  may  occasionally  be  quite  marked.  The 
importance  of  competition  as  a  source  of  error  in  tests  of  pure  line 
selections  of  the  same  variety  merits  detailed  investigation.  If  it  is 
found  that  the  effects  of  competition  between  pure  lines  is  slight  it 
may  be  practicable  to  use  single-row  plots,  or  at  any  rate  to  use  3-row 
plots  without  discarding  border  rows.  The  latter  method  will  reduce 
the  error  from  competition  materially,  without  necessitating  the  loss 
of  any  of  the  experimental  area.  When  the  same  total  area  is  used, 
however,  single  row  plots  are  somewhat  more  reliable  than  3-row 
plots,  because  more  replications  can  be  used.  The  best  size  of  plot  for 
ordinary  variety  testing,  as  indicated  by  this  investigation,  is  probably 
the  3-row  plot  with  border  rows  discarded.  The  length  of  the  plot 
as  harvested  is  assumed  to  be  16  feet,  but  the  same  considerations  will 
apply  for  any  other  convenient  length.  The  number  of  replications 
will  vary  with  the  heterogeneity  of  the  field  and  the  degree  of  precision 
required  (and,  to  some  extent,  with  the  season  and  the  variety), 

Check  plots  have  been  used  in  preliminary  variety  tests  mainly 
for  the  following  purposes: 

(1)  For  the  adjustment  of  the  yields  of  the  test  plots,  and 

(2)  To  provide  a  measure  of  plot  variability  for  the  field  used, 
and  thus  to  determine  the  degree  of  precision  of  the  experimental  re- 
sults, or  the  number  of  replications  which  would  be  required  for  a 
given  degree  of  precision. 

In  both  cases  the  behavior  of  the  check  variety  is  the  basis  for 
conclusions  regarding  the  tested  varieties.  This  involves  the  as- 
sumption that  different  varieties  of  the  same  crop  respond  similarly 


Expe:rime:nts  in  Field  Plot  T^chnic  75 

to  varying  conditions.  In  one  case,  reported  in  this  paper,  two  stand- 
ard varieties,  used  as  duplicate  checks,  and  grown  side  by  side  in 
120  distributed  sections  of  a  field,  showed  no  significant  correlation 
in  relative  yield  of  adjoining  plots,  and  differed  so  widely  in  plot  varia- 
bility that  the  number  of  replications  necessary  for  a  given  degree  of 
accuracy  was  more  than  twice  as  great  for  one  check  variety  as  for  the 
other.  Further  investigation  is  necessary  to  determine  how  generally 
such  cases  may  occur,  but  this  single  case  indicates  at  least  a  possible 
source  of  extreme  error  in  the  use  of  check  plots,  either  for  adjust- 
ment of  yield  or  for  the  determination  of  the  probable  error  of  the 
experimental  results. 

For  this  and  various  other  reasons  the  adjustment  of  yields  by 
means  of  check  plots  is  at  present  of  doubtful  value  as  a  general  prac- 
tice. In  some  cases,  however,  such  adjustment  accomplishes  a  great 
improvement  in  the  precision  of  an  experiment,  with  a  relatively  slight 
increase  in  expense.  The  practice  is  more  promising  for  tests  of 
strains  or  selections  of  the  same  variety  than  for  tests  of  different 
types.  A  thorough  study  of  the  use  of  check  plots  in  variety  and  strain 
testing  may  discover  methods  of  overcoming  the  disadvantages,  and 
thus  make  available  an  economical  and  effective  method  of  increasing 
precision.  Meanwhile,  check  plots  should  be  used  cautiously.  Meth- 
ods for  adjusting  yields  and  for  determining  the  extent  of  plot  varia- 
bility without  the  use  of  check  plots  are  available"' ",' and  check 
plots  must  demonstrate  actual  value  if  they  are  to  continue  in  use  in 
variety  tests. 

SUMMARY 

1.  In  variety  and  strain  tests  of  barley,  oats,  and  wheat,  in  five- 
row  blocks,  the  competing  border  rows  of  adjacent  sorts  gave  relative 
yields  often  widely  different  from  those  of  the  interior  rows  of  the 
same  plots. 

2.  Such  competitive  effects  were  much  more  extreme  between 
different  varieties  than  between  different  commercial  strains  of  the 
same  variety. 

3.  A  considerable  error  from  competition  affected  tests  in  rows 
running  north  and  south,  as  well  as  those  in  rows  running  east  and 
west. 

4.  Although  in  general  the  higher  yielding  varieties  were  favored 
in  competition,  the  reverse  frequently  occurred.  In  some  cases  a  ma- 
terial advantage  in  yield  in  the  interior  rows  was  converted  to  a 
material  disadvantage  in  yield  in  the  border  rows. 


76  Missouri  Agr.  Exp.  Sta.  Research  Bulletin  49 

5.  Competing  quality  was  correlated  fairly  consistently  with 
yield  and  with  earliness  of  heading  and  maturity.  No  relation  to 
grain-straw  ratio  was  found  in  the  one  season  in  which  this  charac- 
ter was  determined.  A  significant  correlation  between  competition 
and  height  was  found  in  the  wheat  variety  test  of  1921,  but  the  rela- 
tion of  competition  to  height  was  not  determined  in  the  other  tests. 

6.  In  the  oats  tests  competition  was  most  closely  related  to  earli- 
ness of  heading  and  maturity,  but  was  also  related  to  yield.  In  the 
wheat,  competition  was  related  fairly  closely  to  both  yield  and  earliness. 
In  the  barley  it  was  not  significantly  correlated  with  any  of  the  char- 
acteristics studied,  though  the  relation  to  yield  was  considerably  closer 
than  the  relation  to  any  of  the  other  characteristics. 

7.  In  the  wheat  and  oats  tests  in  which  earliness  and  yield  were 
correlated  with  competition,  earliness  and  yield  were  correlated  quite 
closely  with  one  another. 

8.  Single-row  plots,  protected  from  competition  by  border  rows 
discarded  at  harvesting,  were  somewhat  more  variable  in  yield  than 
3-row  plots  similarly  protected,  but  the  difference  was  not  great 
enough  to  outweigh  their  advantage  in  size.  The  mean  yield  of  five 
replicate  protected  single-row  plots  is  therefore  more  reliable,  under 
the  conditions  of  these  tests,  than  the  mean  yield  of  three  replicate 
protected  3-row  plots,  which  would  occupy  the  same  area  and  require 
considerably  more  labor  in  harvesting  and  threshing. 

9.  There  was  no  consistent  diflference  in  variability  between  3- 
row  and  5-row  plots. 

.10.  Plot  variability  was  increased  with  increase  in  the  size  of  the 
experiment  field.  The  number  of  replications  required  for  a  given 
degree  of  precision,  as  measured  by  the  variability  of  plot  yields,  is 
therefore  increased  somewhat  when  border  rows  are  added  for  the 
control  of  competition. 

11.  The  variability  of  120  distributed  check  plots  of  Kherson  oats 
diflfered  widely  from  that  of  120  distributed  plots  of  Red  Rustproof 
oats,  adjacent  to  them.  If  the  variability  of  the  check  yields  were  con- 
sidered a  measure  of  the  precision  of  the  test,  entirely  different  con- 
clusions would  be  drawn  on  the  basis  of  the  yields  of  these  two  check 
varieties. 

12.  Adjustment  of  plot  yields  on  the  basis  of  the  yields  of  check 
plots  resulted  in  a  decrease  in  plot  variability  in  three  tests  and  in  an 
increase  in  five  tests.  In  general  the  practice  was  effective  on  fields  of 
high  plot  variability,  and  was  ineffective  on  fields  of  low  plot  varia- 
bility. 


Experiments  in  FieIvD  Plot  Technic  17 

13.  In  the  oats  strain  test  in  which  both  Kherson  and  Red  Rust- 
proof check  plots  were  included,  the  Kherson  check  was  more  eifect- 
ive  than  the  Red  Rustproof  check  as  a  basis  for  adjusting  the  yields  of 
the  Kherson  strains,  while  the  Red  Rustproof  check  was  more  ef- 
fective as  a  basis  for  adjusting  the  yields  of  the  Red  Rustproof  strains. 

14.  The  correlation  between  the  yields  of  adjacent  Kherson  and 
Red  Rustproof  check  plots  was  not  statistically  significant.  Adjust- 
ment of  the  yields  of  the  Kherson  check  plots  on  the  basis  of  the 
yields  of  the  adjacent  Red  Rustproof  plots,  and  of  those  of  the 
Red  Rustproof  plots  on  the  basis  of  the  Kherson  yields  increased  va- 
riability. 


ACKNOWLEDGMENT 

The  writer  is  indebted  to  Professors  M.  F.  Miller  and  W.  C. 
Etheridge  for  a  critical  reading  of  the  manuscript,  and  to  O.  W. 
Letson  for  preparing  figure  8. 


78  Missouri  Agr.  Exp.  Sta.  Re:se:arch  Bui^letin  49 


REFERENCES  CITED. 

1.  Day,  James  W.     The  relation  of   size,   shape,   and  number  of   replications 

of  plats  ta  probable  error  in  field  experimentation.  In  Journ.  Amer.  Soc. 
Agron.  12,  3 ;  pp.  100-105.    1920. 

2.  Etheridge,  W.  C.    A  classification  of  the  varieties  of  cultivated  oats.     Cor- 

nell  Univ.   Agr.   Expt.   Sta.   Memoir   10;   pp.   85-172.     1916. 

3.  Hall,  A.  D.  and  E.  J.   Russell.     Field  trials  and  their  interpretation.     In 

Jour.  Bd.  Agr.  (London)   Supplement:  pp.  5-14.  1911. 

4.  Hayes,  H.   K.  and  A.   C.  Arny.     Experiments   in   field  technic  in  rod-row 

tests.    In  Jour.  Agr.  Res.,  11,  9 :  pp.  399-419.  1917. 

5.  Kiesselbach,  T.  A.  Studies  concerning  the  elimination  of  experimental  error 

in  comparative  crop  tests.  Nebr.  Agr.  Expt.  Sta.  Res.  Bui.  13:  pp.  3-95. 
1918. 

6.  Kiesselbach,  T.  A.    Experimental  error  in  field  trials.    In  Journ.  Amer.  Soc. 

Agron.    11,  6:  pp.  235-241.     1919. 

7.  Kiesselbach,  T.  A.     Plat  competition  as  a  source  of  error  in  crop  tests.    In 

Journ.  Amer.  Soc.  Agron.     11,  6:  pp.  242-247.     1919. 

8.  Love,  H.  H.     The  experimental  error  in  field  trials.     In  Journ.  Amer.  Soc. 

Agron.     11,  5:  pp.  212-216.     1919. 

9.  Love,  H.  H.  and  W.  T.  Craig.    Methods  used  and  results  obtained  in  cereal 

investigations  at  the  Cornell  Station.    In  Journ.  Amer.   Soc.  Agron.  lo, 
4:  pp.  145-157.     1918. 

10.  Lyon,  T.  L.    A  comparison  of  the  error  in  yield  of  wheat  from  plats  and 

from  single  rows  in  multiple  series.    In  Proc.  Amer.  Soc.  Agron.  2:  pp. 
38,  39.     1911. 

11.  Lyon,  T.  L.     Some  experiments  to  estimate  errors  in  field  plat  tests.     In 

Proc.  Amer.  Soc.  Agron.  3:  pp.  89-114.     1912. 

12.  Mercer,  W.  B.  and  A.  D.  Hall.    The  experimental  error  in  field  trials.    In 

Journ.  Agr.  Sci.  4,  2 :  pp.  107-132.    1911. 

13.  Montgomery,  E.  G.     Variation  in  yield  and  methods  of  arranging  plats  to 

secure  comparative  results.     In  25th  Ann.  Rpt.  Nebr.  Agr.   Expt.   Sta.: 
pp.  164-180.     1911. 

14.  Montgomery,   E.   G.     Experiments   in  wheat  breeding.     Experimental  error 

in  the  nursery  and  variation  in  nitrogen  and  yield.    U.  S.  Dept.  Agr.  Bur. 
Plant  Indus.  Bui.  269 :  pp.  5-61.    1913. 

15.  Morgan,  J.  O.     Some  experiments   to  determine  the  uniformity  of   certain 

plats  for  field  tests.    In  Proc.  Amer.  Soc.  Agron.  1:  pp.  58-67.     1910. 

16.  Salmon,  C.     Check  plats  as  a  source  of  error  in  varietal  tests.     In  Journ. 

Amer.  Soc.  Agron.  6,  3:  pp.  128-131.     1914. 

17.  Surface,   F.   M.   and   Raymond   Pearl.     A   method   for   correcting   for    soil 

heterogeneity  in  variety  tests.    In  U.  S.  Dept.  Agr.  Journ.  Agr.  Res.  5, 
22:  pp.  1039-1049.     1916. 

18.  Wood,   T.   B.   &    F.   J.   M.    Strattoii.     The   interpretation   of    experimental 

results.    In  Journ.  'Agr.  Sci.  3,  4 :  pp.  417-440.     1910. 


BIOGRAPHICAL     NOTE 

Lewis  John  Stadler,  born  in  St.  Louis,  Missouri,  July  6,  1896, 
attended  the  University  of  Missouri  during  the  years  1913-1915,  and 
the  University  of  Florida  during  the  year  1916-1917;  and  was  gradu- 
ated from  the  latter-named  institution  in  1917  with  the  degree  of 
Bachelor  of  Science  in  Agriculture.  He  pursued  graduate  studies 
in  field  crops,  botany,  plant  breedin'g,  and  soils  at  the  University  of 
Missouri  and  for  a  term  at  Cornell  University,  during  the  years  1917- 
1922,  holding  a  fellowship  in  cereal  crop  improvement  at  the  Univer- 
sity of  Missouri  in  the  scholastic  year  1917-1918,  and  receiving  the 
degree  of  Master  of  Arts  in  1918.  Since  May  1920  he  has  been  As- 
sistant Professor  of  Field  Crops  at  the  University  of  Missouri. 


f 


(79) 


I  O     DvJOO^ 


^73502 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


